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Trng THCS Phc An GV: Nguyen Viet Vy

Chng 1 : PHEP NHAN VA PHEP CHIA CAC A THCNgay son :12 / 08/ 2011Tiet : 1

I. MUC TIEU :1)Kien thc:

HS nam c quy tac nhan n thc vi a thc.2)Ky nang:HS thc hien thanh thao phep nhan n thc vi a thc.

3)Thai o:- Ren tnh can than , chnh xac , nhanh nhen, hp tac trong hoat ong thao luan.

II. CHUAN B :1) Chuan b cua giao vien:

* o dung day hoc: Bai Soan SGK Bang phu ghi bai tap cung co* Phng an to chclp hoc: Thao luan nhom nho di s gi y giao vien ket hp viap dung k thuat day hoc theo khan trai bai.

2)Chuan b cua hoc sinh:* On lai cac kien thc: n thc ; a thc ; nhan mot so vi mot tong. Nhan hai luytha cung c so SGK dung cu hoc tap.

III. HOAT ONG DAY HOC :1)On nh tnh hnh lp: (1phut)kiem dien va nhac cach hoc bo mon.2)Kiem tra bai cu: (5phut)

*Nhac lai kien thc cu:n thc la g ? a thc la g ?Quy tac nhan hai luy tha cung c so .Quy tac mot so nhan vi mot tong.* Phng an tra li:-n thc labieu thc ai so ch gom mot so, hoac mot bien hoac mot tch gia cac cacso va cac bien.-a thc la tong cua nhng n thc. Moi n thc trong tong goi lamot hang tcua athc o.-Nhan hai luy tha cung c so : am.an= am+n- Nhan vi mot tong: a(b + c) = ab + ac

3) Giang bai mi:* Gii thieu bai: (1phut)Ta a hoc mot so nhan vi mot tong : A (B + C) = AB + AC. Neu goi A la n thc ; (B+ C) la a thc th quy tac nhan n thc vi a thc co khac g vi nhan mot so vimot tong khong ? GV vao bai mi* Tien trnh bai day:

TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dung8ph Hoat ong 1: Nhan biet qui

tac:GV a ra v du ?1 SGK+ Hay viet mot n thc vamot a thc

+ Hay nhan n thc o vitng hang t cua a thc va

Hoat ong 1: Biet quy tac.

HS oc bai ?1 SGKnhom thao luan:

Viet mot n thc va mot athc tuy y vao bang nhom

1 Quy tac:

a) V du :4x . (2x2+ 3x 1)

= 4x.2x2

+ 4x.3x + 4x (1)= 8x3+ 12x24x


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TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dungviet+ Cong cac tch tm c- Gv kiem tra ket qua vainhomGV lay v du SGK

GV goi 1 HS ng tai chotrnh bay. GV ghi bang

GV gii thieu :8x3 + 12x2 4x la tch cuan thc 4x va a thc2x2+ 4x 1Hoi : Muon nhan mot nthc vi mot a thc ta lamthe nao ?

- Kiem tra ket qua

HS(TB-K): ng tai cho

trnh bay. Chang han4x(2x2+ 3x 1)= 4x.2x2+ 4x.3x + 4x (1)

= 8x3+ 12x24x

HS(Y):neu quy tac SGK

Mot vai HS nhac lai

b) Quy tacMuon nhan mot n thc vimot a thc ta nhan n thcvi tng hang t cua a thcroi cong cac tch vi nhau.

15ph Hoat ong 2:Ap dung quytacGV a ra v du SGK lamtnh nhan :

(2x3)(x2+ 5x 2

1 )

BP: ?2GV cho HS thc hien ?2

(3x3y 2

1 x2+5

1 xy).6xy3

GV goi 1 vai HS ng taicho neu ket quaGV ghi bang va cung co quytac GV treo bang phu ghi ebai ?3 GV cho HS hoat ongnhom Goi ai dien cua nhomtrnh bay ket qua cua nhommnhGV nhan xet chung va sasai

Hoat ong 2: lam v du apdungHS(TB):len bang thc hien.Ca lp nhan xet va sa sai

Ca lp lam vao v

Mot vai HS neu ket quaCa lp nhan xet va sa sai

HS(Y): oc e bai ?3

Nhom thao luan:((khan trai

ban)Bao cao ket quaai dien nhom HS trnh bayket quaCac HS khac nhan xet anhgia ket qua cua nhom ban

2. Ap dung :v du : Lam tnh nhan

(2x3)(x2+ 5x 2

1 )

= (2x3).x2 + (2x3).5x +

(2x3). (2

1 )

= 2x310x4+ x3

?2: Lam tnh nhan

(3x3y 2

1 x2+5

1 xy).6xy3

=3x3y.6xy3+(-2

1 x2).6xy3+

+5

1 xy.6xy2=

=18x4y43x3y3+5

6 x2y4

?3: ta co :

* S =2

2)].43()35[( yyxx +++

= (8x+3+y)y

= 8xy+3y+y2* Vi x = 3 met ; y = 2 metTa co :S = 8 . 3 . 2 + 3 . 22

= 48 + 6 + 4 = 58m2

13ph Hoat ong 3: Cung coHng dan hoc nha:GV cho HS lam bai 1 tr 5

a/ x2(5x3x 2

1 )

c) (4x35xy + 2x)(2

1 xy)

Hoat ong 3: giai bai tapHS ca lp lam vao v2HS len bang :HS1 (TB): cau aHS2(TB):cau c

Bai 1 tr 5 SGK:

a/ x2(5x3x 2

1 )

= 5x5x32

1 x2

c/ (4x35xy + 2x)(2

1 xy)


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TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dungGV nhan xet va sa sai

GV cho HS lam bai 2a tr 5a/ x(x y) + y (4 + y)vi x = 6 ; y = 8

GV treo bang phu ghi e bai6 tr 6Goi 1HS ng tai cho traliYeu cau neu cach lamGV goi HS nhac lai quytac

Hng dan hoc nha:Bai 4/5- Goi x la tuoi cua mnh kx > 5ta co:[(x + 5)2 + 10]5 100 = 10xt o tm x

HS ca lp cung lam

HS (K)len bang

Cac HS khac nhan xet vasa sai

HS : ca lp quan satSuy ngh ... HS(TB): ng tai cho ienvao o trong va neu cach lamCac hoc sinh khac nhan xet

HS thc hien cac bc giaitheo s hng dan GVX = 10

= 2x4y +2

5 x2y2x2y

Bai 2a tr 5 SGKa/ x(x y) + y (x + y)= x2xy + xy + y2

= x2+ y2vi x = 6 ; y = 8Ta co : (6)2+ 82= 100Bai 6 tr 6 SGK:

Gia tr : ax (x y) + y3(x+ y)Tai x = 1 ; y = 1 la :

a- a + 2

- 2a2a x

4)Dan do hoc sinh chuan b cho tiet hoc tiep theo(2 phut)Hoc thuoc quy tac nhan n thc vi a thc.

Lam cac bai tap : 1b; 2b ; 3 ; 4 ; 5 tr 5 6 SGKRabai tap nang cao: chng to rang gia tr cua bieu thc sau khong phu thuoc vao bien.a) x(5x 3) x2(x 1)+ x(x2 6x) -10 + 3xb) x(x2+x +1) x2(x + 1) x + 5.On lai a thc mot bien- Chuan b bai nhan a thc vi a thc

IV RUT KINH NGHIEM - BO SUNG......................................................................................................................................................................................

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Ngay soan: 16 /08 /2011

Tiet 2.

I . MUC TIEU :1)Kien thc :

HS nam vng quy tac nhan a thc vi a thc.HS biet trnh bay phep nhan a thc theo cac cach khac nhau.2)Ky nang:

- Ren k nang nhan chnh xac.3)Thai o :

- Can than chnh xac trong tnh toanII. CHUAN B :1)Chuan b cua giao vien:

* o dung day hoc: Bai Soan SGK Bang phu.* Phng anto chc lp hoc: Thao luan nhom nho lay hoc sinh lam trung tam.

2) Chuan b cua hoc sinh:* Bang nhom. Thc hien hng dan tiet trc.III. HOAT ONG DAY HOC:1.On nh tnh hnh lp: (1phut)Kiem dien2.Kiem tra bai cu: (5phut)

HS1:Phat bieu quy tac nhan n thc vi a thc

Ap dung lam tnh nhan : (3xy x2+ y) .3

2 x2y

HS2: a) Thc hien phep nhan, rut gon, tnh gia tr bieu thc

x(x2y) x2(x + y) + y(x2x) tai x =2

1 va y = 100

b) Tm x biet : 3x (12x 4) 9x (4x 3) = 30.

HS1ap so: 2x3y23

2 x4y +3

2 x2y2

HS2 a) ap so: 2xy = 2.2

1 .(100) = 100

b) ap so: x = 23) Giang bai mi* Gii thieu bai: (1 phut)

Cac em a hoc quy tac nhan n thc vi a thc. Ta co the ap dung quy tac nay e

nhan a thc vi a thc c khong ? GV vao bai mi .* Tien trnh bai dayTG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dung6ph H 1 : Hnh thanh quy

tac nhan hai a thc:GV cho HS lam v du :(x 2) (6x25x + 1)GV gi y :+ Em nao thc hien cphep nhan

Hoat ong 1:Hieu qui tac

HS suy ngh lam ra nhap

HS(K): thc hien

1 Quy tac:a) V du : Nhan a thc x 2vi a thc (6x25x + 1)

Giai= x (6x25x +1)2(6x25x +1).

= x .6x2+ x(-5x) +x.1+(-2).6x2+(-2)(-5x) + (-2).1


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TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dung

GV : nhan a thc vi a talam the nao?

Hoi : Em co nhan xet g vetch cua hai a thc ? GV cho HS lam bai ?1lam phep nhan

(2

1 xy 1)(x32x 6)

cho HS nhan xet va sasai Trong qua trnh nhan taco the bo qua bc trunggian

Suy ngh neu quy tac nhSGK1 vai HS nhac lai quy tac

HS(K)nhan xet

Nhom thao luan:Ap dung quy tac thc hien

phep nhan, ket qua:

(2

1 xy 1)(x32x 6)

=2

1 x4yx2y 3xy x3+2x+ 6

= 6x35x2+ x 12x2+10x 2= 6x317x2+ 11x 2* Quy tac :Muon nhan mot a thc vi

mot a thc ta nhan moi hang

t cua a thc nay vi tnghang t cua a thc kia roi

cong cac tch vi nhau.

5ph Hoat ong 2 : Cach 2 cuaphep nhan hai a thcGV gii thieu cach nhanth hai cua nhan hai athc

Hoi : Qua v du tren emnao co the tom tat cach

giai

Hoat ong 2:

HS : nghe giang

HS(TB) : neu cach giai nhSGK

* Chu y:6x25x +1

x 212x2+10x 2

6x35x2+ x6x317x2+ 11x 2

Tom tat cach trnh bay+ a thc nay viet di a thc kia

+Ket qua cua phep nhan moi hangt cua a thc th hai vi a thcthu nhat c viet rieng trong motdong

+ Cac n thc ong dang cxep vao cung mot cot

+ Cong theo tng cot14ph Hoat ong 3 : Ap dung

quy tac:

GV cho HS lam bai ?2lam tnh nhana) (x + 3)(x2+ 3x 5)b)(xy 1)(xy + 5) GV goi 2 HS len bangtrnh bay GV goi HS nhan xet vasa sai* GV chot lai : Cach thhai ch thuan li oi vi a

thc mot bien v khi xepcac a thc nhieu bien theo

Hoat ong 3:giai bai tap apdung

HS : ghi e bai vao v2 HS len bang giaiHS1(TB) :Cau aHS2(TB-Y):Cau b(yeu cau HS lam 2 cach)

HS : nhan xet va sa sai

2Ap dung:?2 :

a) (x + 3)(x2+ 3x 5)= x3+ 3x25x + 3x2+ 9x 15= x3+ 6x2+ 4x 15b)(xy 1)(xy + 5)= x2y2+ 5xy xy 5= x2y2+ 4xy 5

+


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TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dungluy tha tang dan hoacgiam dan ta phai chon bienchnhGV treo bang phu ghi ebai ?3

GV goi HS trnh bay cachgiai

Ca lp oc e bai

HS trnh bay. HS khacnhan xet va sa sai

?3:Ta co (2x + y)(2x y)= 4x22xy + 2xy y2Bieu thc tnh dien tch hnhch nhat la : 4x2y2

- Neu x = 2,5m ; y = 1m th dientch hnh ch nhat :

4 (2

5 )212= 24 (m2)

12ph Hoat ong 4 : Cun g coHng dan hoc nha:- Neu qui tac nhan a thcvi a thc.cho HS lam bai tap 7 (8)SGK

GV goi 1HS len bangGV goi HS nhan xet?: T cau b, hay suy ra ketqua phep nhan

GV treo bang phu ghi ebai 9 tr 8 SGK

GV goi 1 HS ng taicho oc ket qua va ienvao bang phu.Hng dan hoc nha:Bai 12 : Lam tnh nhan ;thu gon cac hang t ongdang. Thay gia tr xBai 14: Gi y: Viet 3 so tnhien lien tiep chan : x ; x+ 2 ;x + 4 va lap hieu :(x + 2)(x + 4)(x + 2) x =192 T o tm c gia trx

Hoat ong 4: Giai bai tap

HS(Y-K):Neu qui tac

HS : oc e bai 7 tr8

HS(TB):len bang trnh bayHS Nhan xet va sa saiHS(TB-K): v (5 x) va (x-5) la hai so oi nen :5 x = (x 5)Nen ch can oi dau cachang t cua ket qua HS : quan sat e bai trenbang phu va suy ngh cachtnh nao cho n gian

HS(TB-K):len bang oc ketqua va ien vao bang phu HS khac nhan xet va sasai

Hs ve nha thc hien cac bcgiai theo hng dan giaovienHS(G):Trnh bai bai giai

Bai 7 tr 8 SGK :a) (x22x + 1)(x 1)= x3x22x2+ 2x + x 1= x33x2+ 3x 1b) (x32x2+ x 1)(5 x)= 5x3x410x2+ 2x3+ 5x x2

5 + x= x4+ 7x311x2+ 6x 5v (5 x) = (x 5)Nen ket qua cua phep nhan :(x32x2+ x 1)( x-5)la:x4- 7x3+ 11x2- 6x + 5Bai 9 tr 8 SGK:ien ket qua tnh c vaobang

Gia tr x va yGia tr B/thc

(x-y)(x2

+xy+y2

)x = 10 ;y = 2 1008x = 1 ;y = 0 1x = 2 ; y = 1 9x=-0,5;y=1,25

64

133

4)Dan do hoc sinh chuan b cho tiet hoc tiep theo: (1 phut)Nam vng quy tac Xem lai cac v duLam cac bai tap : 10 ; 12 ; 13 ; 14 tr 8 9 SGK- Chuan b luyen tap cho tiet tiep theo

IV RUT KINH NGHIEM - BO SUNG


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Ngay soan :20 /08 /2011Tiet : 3I. MUC TIEU :1:Kien thc:

Cung co kien thc ve cac quy tac nhan n thc vi a thc, nhan a thc vi athc.

2:Ky nang: HS thc hien thanh thao phep nhan n , a thc3:Thai o: - Can than trung thc , trong tnh toan.II. CHUAN B :1.Chuan b cua giao vien:

o dung day hoc: Bai Soan SGK SBT- bang phu.- Phng an to chc lp hoc: lay hs lam trung tam.

2.Chuan b cua hoc sinh :- o dung hoc tap:Bang nhom, cac bai tap a dan tiet trc.Hoc thuoc bai va lam bai tap ay u

III. HOAT ONG DAY HOC:1.On nh tnh hnh lp: (1phut)Kiem dien2.Kiem tra bai cu: 5(phut)

HS1: Neu quy tac nhan n thc vi a thcAp dung: Rut gon bieu thc : x(x y) + y(x y) .HS2: Neu quy tac nhan a thc vi a thc

Ap dung: lam phep nhan : (x2y22

1 xy + 2y) (x 2y)

HS1: ap so : x2y2 HS2 :ap so : x3y22

1 xy + 2xy 2x2y3+ xy24y2

3.Ging bai mi:* Gii thieu bai:(1phut)e giup ren k nang thc hien phep nhan a thc vi a thcva s linh hoat trong tnh toan o la yeu cau tiet hoc hom nay.* Tien trnh bai day:

TG Hoat ong cua giao vien Hoat ong cua hoc sinh Ni dung15 Hoat ong 1: Luyen tap

Bai tap 5b tr 6 SGK :GV ghi e bai len bangb) Rut gon bieu thc :xn1(x + y) y(xn1+ yn1)

Goi 1HS kha len bang giai

Bai tap 8b tr 8 SGK:Lam tnh nhanb) (x2xy + y2)(x + y)GV goi 1HS len bang

Bai tap 10 tr 8 SGK:?: Neu cach thc hien ?

Hoat ong 1:

HS: ghi e bai vao v nhapCa lp lam ra nhapHS(K):len bangxn1(x + y)y(xn1+ yn1)= xn1+1 + xn1.y yxn1 yn1+1= xnyn1HS khac nhan xet va sa saiHS : ca lp lam vao vHS(TB)len bang giangb) (x2xy + y2)(x + y)= x2+ x2y x2y xy2+ xy2+ y3= x3+ y2HS(TB-Y):Nhan moi hang tcua a thc nay vi tng hangt cua a thc kia roi cong cac

Dang 1:Thc hien phep tnhBai tap 5b tr 6 SGK :b)xn1(x + y)y(xn1+ yn1)= xn1+1 + xn1.y yxn1yn1+1

= xnyn

Bai tap 8b tr 8 SGKb) (x2xy + y2)(x + y)= x2+x2yx2y xy2+ xy2+ y3= x3+ y2

Bai tap 10 tr 8 SGK :

a) (x22x + 3)(2

1 x 5)


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TG Hoat ong cua giao vien Hoat ong cua hoc sinh Ni dung

a) (x22x + 3)(2

1 x 5)

b) (x22xy + y2)(x y)HS thao luan trnh bay ketqua

Cho lp nhan xetGV sa sai

tchai dien trnh bayHS : ca lp nhan xet va sasai

=2

1 x35x2x2+10x +2

3 x 15

=2

1 x36x2+2

23 x 15

b) (x22xy + y2)(x y)= x3x2y2x2y+2xy2+xy2+ y3= x33x2y + 3xy2+ y3

5 Hoat ong 2: Chng to giatr cua BT khong phu thuocvao bienBai tap 11 tr 8 SGK:

GV cho HS oc e bai 11Hoi : Em nao neu hng giaibai 11goi 1 HS len bang thc hien

Yeu cau nhan xet va sa sai

Hoat ong 2:

HS(Y):oc e bai tap 11HS(TB):Bien oi va thu gon

HS(TB-K): len bang thc hien

1 vai HS nhan xet va sa sai

Dang 2: Chng to gia tr cua BTkhong phu thuoc vao bien

Bai tap 11 tr 8 SGK:Ta co :(x 5)(2x +3)2x(x 3)+x+ 7= 2x2+ 3x 10x 15 2x2+6x + x + 7 = 8.Nen gia tr cua bieu thc

khong phu thuoc vao bien x15 oat ong 3: Giai bai tap tm xBai tap 13 tr 9 SGK:GV cho HS oc e baiHoi : Cho biet cach giai

Goi 1 HS len bang giai Cho lp nhan xet va sa

saiBai tap 14 tr 9 SGK:

Goi HS oc e bai 14Hoi : Em nao neu c cachgiai ?(giao vien gi y)

Goi 1HS len bang giaiCho lp nhan xet va sa sai

Hoat ong 3:

HS(Y-k)oc e baiHS(TB):Thc hien phep nhanva thu gon, chuyen mot vecha bien va mot ve la hangso.HS(TB): len bang giaiCac HS khac nhan xet va sa

sai

HS(Y-k): oc e bai 14HS(K-G): Goi 3 so chan lientiep o la x ; x + 2 ; x + 4Theo e bai ta co :(a + 2) (a + 4) (a + 2) a = 192HS(K-G):len bang giaiHS khac nhan xet va sa sai

Dang 3: Giai bai tap tm xBai tap 13 tr 9 SGK:Ta co :(12x 5)(4x 1) + (3x7)(1 16x) = 8148x212x 20x + 5 + 3x48x27 + 112x = 81

83x 2 = 81 83x = 83 x = 1

Bai tap 14 tr 9 SGK:Goi 3 so chan lien tiep o lax x + 2 ; x + 4Ta co : (x + 2)(x + 4)x(x + 2)= 192x2+ 4x + 2x + 8 x22x = 1924x = 192 8 = 184x = 184 : 4 = 46

Vay ba so t nhien chan lientiep la : 46 ; 48 ; 50

2 Hoat ong4:Cun g coHDVN: Yeu cau HS nhac lai quytac nhan n, a thcHng dan ve nhaBi10 tr 4 SBT (bang phu)

Hoat ong 4:HS(TB): nhac lai 2 quy tacHS Gii bitp theo hng dnGV

Neu bc giai

4.Dan do hoc sinh chuan b cho tiet hoc tiep theo: 1 phut:Xem lai cac bai tap a giaiLam cac bai tap : 12 ; 15 tr 8 9 ; bai 9 ; 10 tr 4 SBT

IV RUT KINH NGHIEM - BSUNG


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Ngay soan: 21 /08 /2011Tiet 4:

I. MUC TIEU :1)Kien thc:

Nam c cac hang ang thc : Bnh phng cua mot tong, bnh phng cua mot hieu

; hieu hai bnh phng.2)Ky nang:Biet ap dung cac hang ang thc tren e tnh nham, tnh hp ly.

3)Thai o:- Phat huy tnh tch cc linh hoat sang tao cu hoc sinh.

II. CHUAN B :1.Chuan b cua giao vien:

o dung day hoc: - Bai Soan SGK SBT Bang phu hnh 1 (9)- Phng an to chc lp hoc: Lay hoc sinh lam trung tam. Phan tch tong hp.

2).Chuan b cua hoc sinh:

- Bang nhom va cac dung cu hoc tap,- Hoc thuoc bai va lam bai tap ay uIII. HOAT ONG DAY HOC :1.On nh tnh hnh lp: (1phut)Kiem dien2.Kiem tra bai cu: (5phut )

HS1(TB-K): Lam bai 15 tr 9 SGK Lam tnh nhan : a) (2

1 x + y)(2

1 x + y).

HS2:(Y) Ap dung quy tac nhan hai a thc : (a + b)(a + b)ap so:

4

1 x2+ xy + y2

ap an (a + b) (a + b) = a2

+ ab +ab + b2

= a2

+ 2ab + b2

3) Giang bai mi:* Gii thieu bai:(1 phut) GV : (a + b) (a + b) = (a + b) 2goi la hang ang thc angnh. Hang ang thc ang nh co rat nhieu ng dung trong toan hoc vao bai mi* Tien trnh biday:

TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dung7 Hoat ong 1: Bnh phng

cua mot tong:GV Qua kiem tra bai cua HS2(a + b) (a + b) = (a + b)2

= a2 + 2ab + b2 goi la bnhphng cua mot tong.Hoi : Neu A ; B la 2 bieu thctuy y ta cung co :(A + B)2= ?GV cho HS lam bai ?2

GV cho HS ap dung tnh :a) (a + 1)2 =b) x2+ 4x + 4 =c) 512; 3012 = ?

Hoat ong 1:

HS : nghe GV gii thieu

HS(TB):Tra li :(A + B)2= A2+ 2AB + B2

HS(TB):Bnh phng cua 1tong hai bieu thc bang bnhphng so th nhat cong ...HS(TB): ong thi len bangbnhHS1: cau aHS2: cau b

1. Bnh phng cua mottong

Vi A ; B la cac bieu thc

tuy y, ta co :(A + B)2= A2+ 2AB + B2

*Ap dung :

a) (a + 1)2= a2+ 2a + 1b) x2+ 4x + 4 = (x + 2)2


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TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dung

BP: ien vao cho trong(+ 5y)2 = 4x2 + 20xy +

(A + )2

= 2AB + B2

GV gii thieu hang ang thcmi

HS3: cau c

HS(TB)(2x+ 5y)2= 4x2+ 20xy + 25y2[A + (-B)]2= A2 2AB + B2

c) 512= (50 + 1)2= 2500 + 100 + 1= 2601

3012= (300 + 1)2= 90000 + 600 + 1

= 90601

7 H 2 : Bnh phng cua mothieu: T o GV gii thieu Hangang thc th (2)Hoi : Vi hai bieu thc A ; Btuy y, ta co (A B)2= ?

GV yeu cau HS phat bieuthanh li GV cho HS lam bai tap apdung

Hoat ong 2:

HS nghe gii thieu

HS(TB):Tra li :(A B)2= A22AB + B2

HS phat bieu thanh li

HS1: cau aHS2: cau bHS3: cau c

2. Bnh phng cua mothieu:Vi A ; B la hai bieu thctuy y ta co :(A B)2= A22AB + B2

* Ap dung:a) (x

2

1 )2= x2x +4

1

b)(2x3y)2=4x212xy + 9y2c) 992= (100 1)2

= 10000 200 + 1= 9800 + 1 = 9801

8 Hoat ong 3:Hieu hai bnhphng: GV cho HS lam bai ?5 ap

dung quy tac nhan a thc :Lam phep nhan :(a + b) (a b)

Hoi : Vi A ; B la 2 bieu thctuy y th :A2B2= ? GV yeu cau HS phat bieuthanh li GV cho HS lam bai tap ap

dunga) (x + 1)(x 1)b) (x 2y)(x + 2y)c) Tnh nhanh : 56 . 64

Hoat ong 3:

HS(TB):len bang giai(a + b) (a b)= a2ab + ab b2= a2b2HS(TB):Tra li :A2B2= (A +B) (A B)

HS(TB-Y):phat bieu thanh lihieu hai bnh phngHS len bang giai (cau c GV

co the gi y)HS1(TB):cau aHS2(TB): cau bHS3(TB): cau c

3.Hieu hai bnh phng:

Vi A va B la hai bieu thctuy y, ta co :A2B2= (A +B)(A B)

Ap dung :

a) (x + 1)(x 1) = x2

1b) (x2y)(x + 2y) = x24y2c) 56 . 64 = (60 4)(60 +4)

= 60242= 3600 16 = 3584

Chu y:(A + B2) = (B A)2

15 Hoat ong 4: Cung coHngdan hoc nha:(BP) ?7

x210x + 25 = (x 5)2x210x + 25 = (5 x)2

Hoat ong 4:Nhom thao luanap dung hang ang thc tnh :

(5 x)2= 25 10x + x2Vay Hng neu nhan xet sai


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TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dungHng neu nhan xet nh vayung hay sai ?Hoi : Sn rut ra c hang angthc nao ?bai tap 17 tr 11 SGK:

GV goi 1 HS len bang giaiGV hng dan ap dungTnh : 252ch can tnh :2 . (2 + 1) = 6 roi them so 25vao ben phaiYeu cau HS nham 352Bai tap 18 tr 11 SGK Goi 1HS ng tai cho ienvao ..., GV ghi bangHng dan hoc nha:

Bai 25a) a ve dang (A + B)2 trongo A = a + b ; B = Cb) a ve dang (A B)2 trongo A = A B ; B = Cc) a ve dang (A + B)2hoac(A B)2trong o A = a hoac

A = a + b= b c hoac B = C

HS(TB):Ket qua :(A B)2= (B A)2

HS ca lp lam ra nhap

HS(TB):len bang trnh bayHS : ngheGV hng dan cach tnh nham

HS(Y): nham 3 . 4 = 12Vay : 352= 1225

HS : ca lp suy ngh

HS(TB-K):ng tai cho tra li

HS thc hien bai giai theo shng dan gv

Bai 17 tr 11 SGK:Ta co : (10a + 5)2= 100a2= 100a + 25

= 100a (a + 1) + 25Ap dung tnh :252= 625352= 1225652= 4225752= 5625Bai 18 tr 11 SGK:a) x2+ 6xy + 9y2= (x+ 3y)2b)x210xy +25y2= (x5y)2

4.Dan do hoc sinh chuan b cho tiet hoc tiep theo: (1 phut) Hoc thuoc ba Hang ang thc : Bnh phng cua mot tong, bnh phng cua mot

hieu, hieu hai bnh phngLam cac bai tap : 16 ; 20 ; 23 ; 24 ; 25, chuan b luyen tap cho tiet sau.

IV RUT KINH NGHIEM-BO SUNG.......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................


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Ngay soan: 26 / 08 / 2011Tiet 5

I. MUC TIEU :1)Kien thc :

Cung co kien thc ve cac hang ang thc : Bnh phng cua mot tong, bnh phng

cua mot hieu, hieu hai bnh phng2)Ky nang:HS van dung thanh thao cac hang ang thc tren vao giai toan

3)Thai o :- Linh hoat, nhanh nhen trong tnh toan.


* o dung day hoc: Bai Soan SGK SBT , bang phu* Phng an to chc lp hoc: phan tch, tong hp

2.Chuan b cua hoc sinh:

* o dung hoc tap: Bang nhom, but da* Kien thc on: Hoc thuoc bai va lam bai tap ay u da gian tiet trcIII. HOAT ONG DAY HOC :1.On nh tnh hnh lp: (1phut)Kiem dien2.Kiem tra bai cu: (6phut)

HS1: Phat bieu hang ang thc Bnh phng cua mot tongAp dung : Viet bieu thc sau di dang bnh phng cua mot tong x2+ 2x + 1= (x +1)2HS2: Phat bieu hang ang thc sau di dang bnh phng cua mot hieuAp dung : Tnh (x 2y)2 = x24xy + 4y2HS3: Phat bieu hang ang thc hieu hai bnh phngAp dung : Tnh (x + 2) (x 2) =x24Hng dan tra li:HS1:Ly thuyet SGK Ap dung : x2+ 2x + 1 = (x + 1)2

HS2: Ly thuyet SGK Ap dung : (x 2y)2 = x24xy + 4y2

HS3: Ly thuyet SGK Ap dung : (x + 2) (x 2) =x243. Giang bai mi :

* Gii thieu bai(1phut):cac hang ang thc c ap dung nh the nao trong viec giaitoan noi dung tiet hoc hom nay cac em se ro.(1ph)* Tien trnh bai day:

TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dung12 Hoat ong 1: Luyen tap

Bai tap 16 tr 11 : BPGV cho HS oc e bai 16 tr 11.a) x2+ 2x + 1b) 9x2+ y2+ 6xyc) 25a2+ 4b220ab

d) x2x +4

1

goi 2 HS len bang giai

Hoat ong 1:

HS(Y) : oc e bai tap 16 tr11

HS1(TB): cau a ; cHS2(TB): cau b ; d1 vai HS khac nhan xet va

Dang 1:Ap dung cac hangang thc :Bai tap 16 tr 11 :a) x2+ 2x + 1 = (x + 1)2b) 9x2+ y2+ 6xy= (3x)2+ 2.3xy + y2= (3x+y)2c) 25a2+ 4b220ab= (5a)2+ (2b)22.5.2b =(5a + 2b)2

d) x2x +4

1


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Bai tap 22 tr 12 :a) 1012Hoi : bang cach nao e tnh

nhanh ket qua ?GV gi y (100 + 1)2Hoi : Ap dung hang ang thcnao ?GV goi 1 HS ng tai cho traliTng t goi 1HS giai bai b, c

sa sai neu co

HS : suy ngh ...

HS(TB):bnh phng cua mottongHS(TB):ng tai cho tra li

HS(TB):len bang giai

= x22.x.2

1 + (2

1 )2 = (x 2

1 )2

Bai tap 22 tr 12:a) 1012= (100 + 1)2= 10000 + 200 + 1 = 10201

b) 1992

= (200 1)2

= 40000 400 + 1 = 39601c) 47 . 53 = (50 3)(50+3)= 5029 = 2500 9 = 2491

12 Bai 23 tr 12 :GV gi y chng minh :(a + b)2= (a b) + 4ab

+ Tnh (a b)2= ?+ Thu gon :a22ab + b2+ 4ab = ?a2+ 2ab + b2= ?

Tng t goi 1 HS ng taicho neu c/m:(a b)2= (a + b)24ab

Ap dung tnh :

a) (a b)2biet : a + b = 7 ;ab = 12b) (a + b)2biet :a b = 20 ;ab = 3GV goi 1 HS len bang giaiGV nhan xet va sa sai

HS : ca lp oc e bai va suyngh...

HS(TB): a22ab + b2

HS(TB): a2+ 2ab + b2HS(TB): (a + b)2KLHS(TB) : ng tai cho neucach chng minh tng tHS khac nhan xet

HS : oc e baiCa lp suy ngh

HS(K-G):len bang giai HS khac nhan xet va bosung

Dang 2: Ap dung e chngminh bieu thcBai 23 tr 12 :

a) (a + b)2= (a b) + 4abTa co : (a b)2+ 4ab= a22ab + b2+ 4ab= a2= 2ab + b2= (a + b)2

(bang ve trai)b) (a b)2= (a + b)24abTa co : (a + b)24ab= a2+ 2ab + b24ab= a22ab + b2= (a b)2

(bang ve trai)* Ap dunga) (a b)2= 4ab (a + b)2= 4.12 (7)2= 48 49 = 1b) (a + b)2= 4ab (a-b)2

= 4.3 202= 12 400= 112

7 Hoat ong 2:Tnh gia tr bieuthc:

Bai 24 tr 12:49x270x + 25Hoi : Bieu thc co dang hangang thc nao ?Goi 1 HS thc hienCho ca lp nhan xet

Hoat ong 2:

HS ghi e baiHS(TB):Dang (A B)2

49x270x + 25= (7x)22.7x.5 + 52

= (7x 5)2HS(K)Nhan xet

Dang 3:Tnh gia tr bieu thc:Bai 24 tr 12 :

Ta co : 49x

2

70x + 25= (7x)22.7x.5 + 52=(7x 5)2a) x = 5 ta co:(7x 5)2= (7.55)2= 900

b) x =7

1 ta co :

(7x 5) = (7.7

1 5)2= 16

5 Hoat ong 3: Cung coHng dan hoc nha:

Goi HS nhac lai 3 hang angthc a hoc (phat bieu thanhli va neu cong thc)

Hoat ong 3:HS : Phat bieu thanh li vaghi cong thc 3 hang angthc a hoc


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TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dungHng dan hoc nha:On lai cac hang ang thc ahoc* Bnh phng mot tong* Bnh phng mot hieu

* Hieu hai bnh phng

* (A + B)2= A2+ 2AB + B2* (A B)2= A22AB + B2* A2B2= (A +B)(A B)

4.Dan do hoc sinh chuan b cho tiet hoc tiep theo: (1 phut)Lam cac bai tap : 19 ; 21 5tr 12 SGK- Chuan b Bai 4 : Nhng hang ang thc ang nh (tt)

IV RUT KINH NGHIEM - BO SUNG..........................................................................................................................................................................

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Ngay soan: 30/ 08/ 2011Tiet : 6

I. MUC TIEU :1)Kien thc :

Nam c cac hang ang thc : (A + B)

3

; (A B)

3

2)Ky nang:Biet van dung cac hang ang thc tren e giai bai tap

3)Thai o :Ren luyen ky nang tnh toan, can than, hp tac trong hoat ong thao luan


* o dung day hocBai Soan SGK SBT Bang phu* Phng an to chc lp hoc: Neu van e, nhom thao luan

2.Chuan b cua hoc sinh:

* Hoc thuoc bai va lam bai tap ay u* Kien thc on: On cac hang ang thc a hocIII. HOAT ONG DAY HOC :1.On nh tnh hnh lp: (1phut)Kiem dien2.Kiem tra bai cu: (5phut)

HS1: Viet cong thc bnh phng cua mot tongTnh : (a + b) (a + b)2.

HS2: Viet cong thc bnh phng cua mot hieuTnh : (a b) (a b)2.

ap so:a3+ 3a2b + 3ab2+ b3

ap so: a33a2b + 3ab2b3

3. Giang bai mi:* Gii thieu bai:(1phut)e co cach tnh nhanh hn, chung ta hoc tiep bai hang ang thcang nh* Tien trnh bay day:

TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dung12 Hoat ong 1: Tm quy tac

miHoi : T ket qua cua bai(a + b) (a + b)2kiem tra HS1,hay rut ra ket qua cua (a + b)3

Hoi : Hay phat bieu hangang thc tren bang li

Hoat ong 1:Da vao bai kiem tra HS traliHS : ghi(A +B)3=A3 +3A2B+3AB2+ B3

HS : phat bieu hang angthc bang li

4.Lap phng cua mot tong:Vi A ; B la hai bieu thc tuyy, ta co :(A+B)3=A3+3A2B+3AB2+B3

GV cho HS ap dung tnha) (x + 1)3b) (2x + y)3

Goi 1 HS ng tai cho neuket quaGV nhan xet va sa sai

HS : ca lp lam vao bang controng 1

HS(TB):ng tai cho neu ketqua

Ap dung:a) (x + 1)3

= x3 + 3x2 .1 + 3x . 12+ 13= x3+ 3x2+ 3x + 1b) (2x + y)3= (2x)3+3(2x)2y + 3.2xy2+ y3= 8x2+ 12x2y + 6xy2+ y3

14 Hoat ong 2: Tm quy tac

miGV yeu cau HS tnh :

Hoat ong 2:

HS : ca lp tnh ra giay nhap

5.Lap phng cua mot hieu:

Vi A va B la cac bieu thctuy y, ta co :


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TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dung(a b)3= [a + (b)]3 So sanh ket qua vi baikiem tra HS2 Tng t vi A ; B la cacbieu thc ta co : (A - B)3= ?

GV yeu cau HS viet tiep ehoan thanh cong thcYeu cau HS phat bieu thanhliGV cho HS ap dung tnh

a) (x 3

1 )3

GV hng dan HS lam :

(x3

1 )3= x33x2.3

1 +

3x. 91

( 31

)3

= x3x2+

3

1 x 27

1

b) Tnh (x 2y)3Hoi : cho biet bieu thc thnhat ? bieu thc th hai GV yeu cau HS the hientng bc theo hang angthcGV treo bang phu

cau c : Khang nh nao ung :a) (2x 1)2= (1 2x)2b) (x 1)3= (1 x)3c) (x + 1)3= (1 + x)3d) x21 = 1 x2e) (x 3)2= x22x + 9Hoi : Em co nhan xet g vequan he cua (A B)2vi (B A)2; cua (A B)3vi (BA)3

HS(TB):Hai cach lam eu choket qua :(a b)3= a33a2b + 3ab2b3

HS ghi tiep :

= A3

3A2

B + 3AB2

B3

1 vai HS phat bieu thanh li

HS : theo doi GV hng dan

HS : ca lp lam vao v

Tra li : A = x ; B = 2y

Nhom thao luan

Ket quaa) ung v A2= (A)2b) Sai v A3= (A)3c) ung v x + 1 = 1 + xd) Sai v x21 = (1 x2)e) Sai v (x 3)2= x26x + 9

Tra li :(A B)2= (B A)2(A B)3= (B A)3

(AB)3=A33A2B+3AB2B3

Ap dung :

a) (x 3

1 )3

= x33x2.3

1 + 3x.9

1(

3

1 )3

= x3x2+3

1 x 27

1

b) (x 2y)3= x33x2.2y + 3x(2y)2(2y)3= x36x2y + 12xy28y3

11 Hoat ong 3: Cung co:Hay so sanh hang ang thclap phng mot tong va lapphng mot hieu.

Bai tap 26 tr 14:a) (2x2+ 3y)3GV cho ca lp lam vao vGoi 1 HS len bang lam

b) ( 21

x 3)3

GV cho ca lp lam vao v

Hoat ong 3:HS(K):Lap phng mot tongth dau toan bo la dau cong,con lap phng mot hieu thdau cong tr xen ke

Ca lp lam vao vHS(TB-K):len bang lam 1 vai HS khac nhan xet vabo sung

Ca lp lam vao vHS(TB): len bang giai

Bai tap 26 tr 14:a) (2x2+ 3y)3= (2x2)3+ 3(2x2)2.3y +3.2x2.(3y)2+ (3y)3= 8x6+ 36x4y +54x2y2+27y3

b) (2

1 x 3)3

= (2

1 x)33.(2

1 x)2.3 +3.2

1 x.32

33= 81 x3 4

9 x2+ 227 x 27


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TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dungGV goi 1 HS len bang giaiGoi HS nhan xetBai tap 29 tr 14 SGK :

GV treo bang phu ghi ebai 24 tr 14

Yeu cau HS hoat ong theonhomGoi ai dien nhom trnh baybai lam

1 vai HS nhan xet

Hoat ong theo nhom. Nhomtrng chuan b bang nhomai dien nhom trnh bay bai

lamN. x23x2+ 3x 1U. 16 + 8x + x2H. 3x2+ 3x + 1 + x3A. 1 2y + y2

Bai tap 29 tr 14 SGK:(x 1)3 (x + 1)3 (y 1)2

N H A

(x 1)3 (1 + x)3 (1 y)2N H A

(x + 4)2U

4.Dan do hoc sinh chuan b cho tiet hoc tiep theo: (1 phut)On tap nam hang ang thc ang nh a hoc, so sanh e ghi nhLam bai tap 27 28 tr 14 SGK ; bai 16 tr 5 SBT

IV RUT KINH NGHIEM - BO SUNG

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19/507


TG Hot ong Giao vien Hot ng Hc sinh Noi dungYeu cau HS viet tiep ?+ GV gii thieu :(A2 AB + B2) quy c goi labnh phng thieu cua hai bieuthc.

? Em nao co the phat bieu bangli tong hai lap phng cua haibieu thc.* (Bang phu)a)Viet x3+ 8 di dang tch .GV gi y : x3+ 8 = x3+ 23+ Tng t GV goi HS vietdang tch : 27x3+ 1

b) Viet (x + 1) (x2x + 1) dangtong.GV goi 1 HS len bang giai.* GV cho HS lam bai tap 30a(Sgk/16)Rut gon bieu thc(x+3)(x 3x+9) - (54+x3)+ GV nhac nh HS phan biet (A

+B)3

la lap phng cua mottong vi A3+ B3la tong hai lapphng

* HS nghe GV gii thieu cachgoi cua A2AB + B2

HS(TB-K): ng tai cho phatbieu

HS (K):Thc hienx3+ 8 = (x + 2) (x22x + 4)

HS(TB):len bang trnh bay:27x3+ 1 = (3x)3+ 13 =

= (3x + 1)( 9x2 3x + 1)

HS(TB): 1HS len bang trnhbay bai giai

* HS lam bai tap di shng dan cua GV :(x+3)(x3x+9) - (54+x3)= x3+ 3354 x3= x3+ 27 54 x3= 27

tuy y, ta co :A3+B3=(A+B)(A2AB+B2)

* Ap dung:a) x3+ 8 = x3+ 23= (x + 2) (x22x + 4)

b) (x + 1) (x2x + 1)= x3+ 13= x3+ 1

10 ph Hot ng 2:Tm hieuhiu hailp phng.

* GV yeu cau HS lam ?3Tnh (a b)(a2+ ab + b2)

* Tng t, vi A,B la cac bieuthc ta cung co :A3B3 = + GV quy c cach goi(A2+ AB + B2) la bnh phngthieu mot tong

? : Hay phat thanh li angthc hieu hai lap phng cua 2bieu thc

* GV cho HS ap dung tnha) (x 1)(x2 + x + 1)=

Hoat ong 2:* Ca lp lam bai vao v(a b)(a2+ ab + b2) =a3+a2b+ab2a2bab2b3= a3b3

HS(TB-Y): Len bang viettiepA3B3= (AB)(A2+AB+ B2)

HS(TB-K): : Phat bieu thanhli ( bang phu)

* HS: ca lp lam vao v

2.Hieu hai lap phng:

Vi A, B la cac bieu thctuy y taco :A3B3=(AB)(A2+AB+B2)

Ap dung:a) (x 1)(x2+ x + 1)


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21/507


TG Hot ong Giao vien Hot ng Hc sinh Noi dung2)x2 - 14xy + 49y2= (x - 7y )23) (2x +3y )(2x 3y ) =4x2 9y24) ( 3x + y) (9x2 - 3xy + y2 ) =27x3+ y35) ( 2x - 5 ) (4x2 + 10x + 25 )

= 8x3

1256) ( x + 4 )3= x3 + 12x2 +48x + 647) 1-6x + 12x2 - 8x3 = (1 -2x)3

GV: nhan xet sa sai.Hng dan ve nha (bang phu)Bai 34: Ket hp cac hang angthc e rut gon cac bieu thc.Bai 35: 68 . 66 = 2 . 34 . 66 =>dung hang ang thc bnh

phng mot48 . 74 = 2 . 24 . 74tong va bnh phng mot hieu

HS(K-G): Len bang ien ketqua vao cho trong

a) Dung hang ang thc hieuhai bnh phngc) Dung hang ang thc bnhphng mot tong

HS: hoan thanh bai tap theohng dan GV

4.Dan do hoc sinh chuan b cho tiet hoc tiep theo: (1 phut)* Hoc thuoc long 7 hang ang thc ang nh a hoc.* BTVN: 31,32,33,36,37 (Sgk/16,17) va bai 17,18 (Sbt/5)* Chuan b tiet sau luyen tap.

IV RUT KINH NGHIEM BO SUNG:.........................................................................................................................................................................

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Ngay soan 5/9/2011Tiet 8:

I. MUC TIEU :1.Kien thc :Cung co kien thc ve bay hang ang thc ang nh2.Ky nang: HS biet van dung kha thanh thao cac hang ang thc ang nh vao giai toan

Dung hang ang thc (A B)2

e xet gia tr cua mot so tam thc bac hai.3.Thai o : - Yeu thch mon hoc, linh hoat trong tnh toan.II. CHUAN B :1.Chuan b cua giao vien:

* o dung day hoc: Bai Soan SGK SBT Bang phu.* Phng an day: Phan tch tong hp kien thc, giai bai tap.

2.Chuan b cua hoc sinh:*o dung hoc tap: Bang nhom, SBT* Kien thc on: Hoc thuoc bay hang ang thc , lam bai tap ay u.

III. HOAT ONG DAY HOC :

1.On nh tnh hnh lp: (1 phut )2.Kiem tra bai cu: (6 phut)

HS1(TB-Y): Cha bai tap 30(a) tr 16 SGK

ap an : Rut gon : (x + 3)(x23x + 4) (54 x3) = x33354 x3= 27

Cac khang nh sau ay ung hay sai ? (Dung bang phu)

a) (a b)3= (a b)(a2+ ab + b2) (S) ; d) (a b)3= a3b3 (S)

b) (a + b) 3= a3+ 3ab2+ 3a2b + b3() ; e) (a + b) (b2ab + a2) = a3+ b3 ()

c) x2+ y2= (x y)(x + y) (S)

HS2 (TB): - Cha bai tap 37 tr 17 SGK (Dung bang phu)(x y)(x2+ xy + y2) x3+ y3

(x + y)(x t) x3y3

x22xy + y2 x2+ 2xy + y2

(x + y)2 x2y2

(x + y)(x2xy + y2) (y x)2

y3+ 3xy2+ 3x2y + x3 y33xy2+ 3x2y x3

(x t)3 (x + y)3

3. Giang bai mi :* Gii thieu bai: (1phut)Giup thay c ch li cua cac hang ang thc vao viec giai toannh the nao noi dung tiet luyen tap se giup chung ta ro hn.* Tien trnh bai day:


10phHoat ong 1: Luyen tap* Bai 33 tr 16 SGK: GV yeu cau 2 HS len

bang lam baiHS1(TB) : a, c, e

Hoat ong 1:HS : ca lp cung lam2HS len bang lam cac HS

khac m v oi chieu, nhanxet

Dang 1:Rut gon* Bai 33 tr 16 SGK:a) (2 + xy)2= 4 + xy+x2y2

b) (53x)2= 25 30x + 9x2c) (5x2)(5 + x2) = 25 x4


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TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dungHS2(TB-K): b, d, f d) (5x 1)3

= 125x375x2+ 15x + 1e) (2x y)(4x2+ 2xy + y2= 8x3y3

f) (x + 3)(x2

3x + 9)= x3+ 278ph * Bai 34 tr 17 SGK:

GV yeu cau HS chuan bbai khoang 3 phut sau omi 2 HS len bang lam caua, b

Cau c GV yeu cau HS quansat ky bieu thc e phathien ra hang ang thc :A22AB + B2

HS ca lp lam vao nhapHai HS len bang lamHS1(TB):cau a(a + b)2(a b)2= (a + b + a b)(a + b a +b)

= 2a . 2b = 4a.bHS2(TB-K): cau b

HS ca lp quan sat va nhandang ra hang ang thc1 HS len bang thc hien

* Bai 34 tr 17 SGK:a) (a + b)2(a b)2= (a + b + a b)(a + b a + b)= 2a . 2b = 4a.bb) (a + b)3(a b)32b3=[(a+b) (ab)][(a+b)2+(a+b)(ab) + (ab)2] 2b3

= 2b(a2+2ab+b2+a2b2+a22ab +b2) 2b3= 2b(3a2+ b2) 2b3=6a2b + 2b32b3= 6a2bc) (x + y +z)22(x +y + z)(x+y)+(x+y)2

8ph Bai 35 tr 17 SGK:* Hay dung nhng hangang thc tnh nhanh cacbieu thc.GV cho HS hoat ong theonhom

HS hoat ong theo nhomNhom 1, 2, 3 cau aNhom 4 ; 5 ; 6 cau b

Dang 2: Tnh nhanh.Bai 35 tr 17 SGK:a) 342+ 662+ 68 . 66= 342+ 662+ 2 . 34 . 66= (34+66)2= 1002= 10000b) 742+ 24248 . 74= 742+ 2422.25.74= (74 24)2= 502= 2500

10ph Hoat ong 2: Cung coHng dan ve nha:

Nhac lai cac hang angthc ang nhHay phat bieu bang li vaviet lai hang ang thcang nh ?

* Nhac lai phng phapchng minh mot ang thc?

Hoat ong 2:HS: Neu lai 7 hang ang

thc ang nh.HS1(TB-Y): 4 hang angthc auHS2(K): 3 hang ang thccuoiHS(K-G): Gom 3 cachchng minh:+ Bien oi ve trai+ Bien oi ve phai+ Bien oi ca hai ve Bai 38 tr 17 SGK :


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TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dung* Hng dan ve nha:Bai 38 tr 17 SGK:Chng minh cac hang angthc sau:a) (a b)3= (b a)3b) (a b)2= ( a + b)2Gi y: e chung minh cachang ang thc tren ta phaibien oi mot ve

HS: Thc hien cac phep bienoi e chng minh cac hangang thc tren

a) (a b)3= (b a)3ta co : (b a)3== (b33b2a +3ba2a3)= a33a2b + 3ab2b3

= (a b)3

( = ve phai)b) (a b)2= ( a + b)2ta co:(ab)2=(a)22.(a).b + b2= a2+2ab+b2=(a + b)2 (= ve phai)

4.Dan do hoc sinh chuan b cho tiet hoc tiep theo: (1 phut)Lam cac bai tap 31 ; 36 tr 16,17 SGKBai tap danh cho HS kha gioi: 18 ; 19 ; 20 tr 5 SBT* Gi y : Bai 18 : a bieu thc ve dang bnh phng cua 1 tong hay 1 hieu

IV. RUT KINH NGHIEM BO SUNG:..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................


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Ngay 10 thang 9 nam 2011Tiet 9:

I. MUC TIEU :1.Kien thc: - HS hieu the nao la phan tch a thc thanh nhan t

- Biet cach tm nhan t chung va at nhan t chung.

2.Ky nang: - Ren ky nang tnh toan, ky nang phan tch a thc thanh nhan t.3:Thai o : - Yeu thch mon hoc, sang tao trong hoc tap.II. CHUAN B :1.Chuan b cua giao vien:

*o dung day hoc: Bai Soan SGK SBT Bang phu.* Phng an to chc lp hoc: Hoc tap theo nhom.

2.Chuan b cua hoc sinh:*Dung cu hoc tap:Hoc thuoc bai SGK SBT.* Kien thc on: On tap cac hang ang thc a hoc, lam bai tap ay u.

III. HOAT ONG DAY HOC:1.On nh tnh hnh lp: (1phut)Kiem dien2.Kiem tra bai cu: (5phut) Tm gia tr bieu thc

HS1(TB-Y): 85 .12,7 + 15 .12,7 =?V sao viet c tch trenHS2(TB): 52 . 143 52 . 39 8 . 26 =

Phng an tra li 85 .12,7 + 15 .12,7 = 12,5 (85 + 15) = 12,7 . 100 = 127052 . 143 52 . 39 8 . 26 = 52 . 143 52 . 59 4 . 52

= 52 (143 39 4) = 52 . 100 = 52003. Giang bai mi:

* Gii thieu bai: (1phut)T kiem tra bai cu dung tnh chat phan phoi cua phep nhan oi vi phepcong e tnh nhanh co lien quan en kien thc ma noi dung bai hoc hom nay chung ta tm hieu.* Tien trmh bai day:TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dung13 Hoat ong 1:Hnh thanh khai

niem:GV cho HS lam v du 1?Nhan xet g ve cac hang t cuaa thcGV: Gi y : 2x2= 2x . x

4x = 2x . 2? : Em hay viet 2x2 4x thanhmot tch cua cac a thc ?GV trong v du va roi ta viet2x2 4x thanh tch 2x (x 2),viec bien oi o c goi laphan tch a thc 2x24x thanhnhan t.?. The nao la phan tch a thcthanh nhan t ?

GV:v du tren con goi la phan

Hoat ong 1:Nam ckhai niem:

Ca lp lam v du 1HS(TB):Neu nhan xet: Haihang t co chung tha so 2x

HS(TB-Y):viet :2x24x = 2x . x 2x . 2

= 2x (x 2)

HS: nghe GV gii thieu

HS(Y): tra li khai niem nhSGKMot HS khac nhac lai

1 V du:a) v du 1:Hay viet 2x2 4x thanhmot tch cua nhng athc

Giai

2x24x = 2x . x 2x . 2= 2x (x 2)

* Phan tch a thc thanhnhan t (hay tha so) labien oi a thc o thanhmot tch cua nhng athc. Cach lam tren goi laphan tch a thc thanhnhan t bang phng phap

at nhan t chung.


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TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dungtch a thc thanh nhan t bangphng phap at nhan t chung.?: Hay cho biet nhan t chung v du tren?GVcho HS lam tiep v du 2 tr 18

SGK.GV goi 1 HS len bang lam bai,sau o kiem tra bai cua mot soHS khac.

?. Nhan t chung trong v du nayla bao nhieu ??. He so cua nhan t chung coquan he g vi cac he so nguyendng cua cac hang t 15, 5, 10

?. Luy tha bang ch cua nhant chung (x) quan he nh the naovi luy tha bang ch cua cachang t ?* GV a ra cach tm nhan tuchung vi cac a thc co he songuyen.

HS(Y-K): Tra li : 2x

HS: ca lp lam bai vao v

HS(TB):len bang lam15x35x2+ 10x= 5x. 3x25x . x + 5x . 2= 5x (3x2x + 2)HS(Y):nhan t chung la 5x

HS(K-G): nhan xet : He socua nhan t chung chnh laCLN cua cac he so nguyen

dng cua cac he soHS(TB):Phai la luy tha comat trong cac hang t cua athc, vi so mu la so mu nhonhat cua no trong cac hangt.

b) V du 2:Phan tch a thc :15x35x2 + 10x thanhnhan t ?

Giai15x35x2+ 10x= 5x. 3x25x . x + 5x . 2= 5x (3x2x + 2)

12ph Hoat ong 2: Van dung, renluyen ky nang:GV cho HS lam ?1GV hng dan HS tm nhan tchung cua moi a thc, lu y oidau cau c. Sau o GV yeu cau HS lamvao v.Goi 3 HS len bang lam cau b, neu dng lai ket qua(x 2y)(5x2 15x) co c

khong ?* GV nhan manh: Nhieu khi elam xuat hien nhan t chung, tacan oi dau cac hang t ; dungtnh chat A = (A)GV mot trong cac li ch cuaphan tch a thc thanh nhan tla giai bai toan tm xGV cho HS lam ?2Tm x sao cho : 3x26x = 0

GV gi y phan tch3x26x thanh nhan t.

Hoat ong 2: Giai bai tapvan dung

HS : ca lp lam baiHS nghe GV hng dan

HS : lam vao v

3 HS len bang lamHS1: a ; HS2: b ; HS3: cHS(TB): V ket qua o

phan tch cha triet e contiep tuc phan tch c bang5x (x 3)

HS : lam vao v

HS(TB): len bang trnh bay3x(x 2) = 0

2.Ap dung:?1 Phan tch cac a thcthanh nhan ta) x2x = x . x x . 1

= x (x 1)b) 5x2(x2y) 15x (x 2y)= (x 2y)(5x215x)= (x 2y) . 5x (x 3)= 5x (x 2y)(x 3)c) 3(x y) 5x(y x)= 3(x y) + 5x(x y) =

= (x y)(3 + 5x)* Chu y : Nhieu khi elam xuat hien nhan tchung, ta can oi dau cachang t(Ap dung t/c A = (A)

?2:Ta co : 3x26x = 0

3x(x 2) = 0x = 0 hoac x = 2


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Ngay soan: 12/ 09 / 2011Tiet : 10

PHAN TCH A THC THANH NHAN TBANG PHNG PHAP DUNG hang ang thc

I. MUC TIEU :1)Kien thc:HS hieu c cach phan tch a thc thanh nhan t bang phng phap dung hang ang

thc HS biet van dung cac hang ang thc a hoc vao viec phan tch a thc thanhnhan t.

2)Ky nang: - Ren ky nang phan tch tong hp, phat trien nang lc t duy.3)Thai o: - Giao duc tnh can than, linh hoat, yeu tch mon hoc.II. CHUAN B :1. Chuan b cua giao vien:

*o dung day hoc: Bai Soan SGK SBT Bang phu.* Phng an to chc lp hoc: Hoc tap nhom nho.

2. Chuan b cua hoc sinh:*Dung cu hoc tap: Bang nhom SGK SBT* Kien thc on: Lam bai tap ay u, hoc thuoc cac hang ang thc ang nh.

III. HOAT ONG DAY HOC :1.On nh tnh hnh lp: (1phut)Kiem dien2.Kiem tra bai cu: (6phut)

HS1:Tm x biet:a) 5x (x 2000) x + 2000 = 0 ; b) x313x = 0ap an:5x(x 2000) (x 2000) = 0 x(x213) = 0

(x 2000)(5x 1) = 0 x = 0 hoac x2

= 13x = 0 hoac x =5

1 x = 0 hoac x = 13

HS2(TB):Dung bang phuViet tiep vao ve phai e c cac hang ang thcA2+ 2AB + B2 = (A + B)2A22AB + B2 = (A B)2A2B2 = (A + B) (A B)A3+ 3A2B + 3AB2+ B3 = (A + B)3A33A2B + 3AB2B3 = (A B)3

A

3

+ B

3

= (A + B)(A2

AB + B

2

)A3B3 = (A B)(A2+ AB + B2)3. Giang bai mi :

* Gii thieu bai: (1 phut)GV phan tch a thc (x3x) thanh nhan t. ket qua x(x21) th x(x21)= x(x212)= x( x + 1)(x 1) vao bai mi.* Tien trmh bai day:

TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dung16ph Hoat ong 1: Tm kien thc

mi :

* GV: Cac hang ang thc labai toan phan tch a thc

Hoat ong 1:Nam c cachphan tch

1. V du:Phan tch a thc thanh

nhan t :a) x24x + 4


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G Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dungthanh nhan t.GV a ra v du :Phan tch a thc thanh nhan tx24x + 4?.Dung c phng phap at

nhan t chung khong ? V sao ?

?. a thc co 3 hang t em hayngh xem co the ap dung hangang thc nao e bien oi ? GV yeu cau HS thc hienphan tchGV gii thieu cach lam nhtren goi la phan tch a thcthanh nhan t bang phng

phap dung hang ang thc* Tng t oi vi cac cau conlai.GV hng dan HS lam bai ?1a) x3+ 3x2+ 3x + 1?. a thc nay co 4 hang t emco the ap dung hang ang thcnao ?* Yeu cau HS trnh bay baigiai.

b) (x + y)29x2GV gi y :(x+y)29x2= (x+y)2(3x)2Vay bien oi tiep nh the nao?GV yeu cau HS lam tiep ?2

Ca lp oc e bai va suy ngh

HS(TB-K): Khong dung c

v tat ca cac hang t cua athc khong co nhan t chungHS(K) : a thc tren co theviet c di dang bnhphng cua mot hieu.HS(TB):x24x + 4= x22.x.2 + 22= (x 2)2HS: nghe gii thieu

HS : suy ngh va len bangtrnh bayHS ca lp quan sat e baiHS(TB): co the dung hangang thc lap phng cua mottongHS ca lp lam vao giay nhap

HS(TB) :bien oi tiep= (x + y + 3x)(x + y 3x)= (4x + y)(y 2x)Nhom hoat ong ?21HS len bang trnh bay

b) x22c) 1 8x3

Giai :a) x24x + 4= x22x . 2 + 22= (x 2)2

b) x2

2 = x2

( 2 )= (x 2 )(x + 2 )c) 1 8x3= 13(2x)3= (1 2x) (1 +2x + 4x2)* Cach lam nh tren goi la

phan tch a thc thanhnhan t bang phng phapdung hang ang thc

?1:a) x3+ 3x2+ 3x + 1= x3+ 3x2.1 + 3x. 12+ 13= (x + 1)3

b) (x + y)29x2= (x + y)2(3x)2= (x + y + 3x)(x + y 3x)

= (4x + y)(y 2x)?2 :105225 = 105252= (105 + 5)(105 5)= 110 . 100 = 11000

5ph Hoat ong 2: Ap dung:

GV cho v du : CMR :(2n + 5)2 25 chia het cho 4

vi moi so nguyen?. e c/m a thc chia het cho4 vi moi so nguyen n, can lamthe nao ?* Nh vay ta phai bien oi athc thanh mot a thc la boicua 4.Goi HS len bang lam

Hoat ong 2:Giai bai tap apdungHS : ca lp ghi e vao v

HS(K-G):can bien oi a thcthanh mot tch trong o co thaso la boi cua 4

HS(k):len bang giai

2.Ap dung:V du : c/m rang :(2n + 5)2 25 M 4 vi moiso nguyen n.

GiaiTa co : (2n + 5)225= (25n + 5)252= (2n(2n + 10) = 4n( n + 5)= 2n(2n + 10) = 4n(n + 5)nen : (2n + 5)225 M4

15ph Hoat ong 3: Cung co valuyen tap:

* Bai 43 tr 20 SGK:GV cho HS lam bai 43 ; HS

Hoat ong 3: Giai bai tap

HS : ca lp cung lam vao giay

Luyen tap* Bai 43 tr 20 SGK:

a) x2

= 6x + 9= x2+ 2x.3 + 32


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TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dunglam bai oc lap, roi lan lcgoi HS len bang trnh bayGV gi y : nhan xet a thcco may hang t e la chonhang ang thc ap dung cho

phu hp.GV cho HS nhan xet bai lamcua banGV sa sai* Bai 44 b ; e tr 20 SGK :GV cho HS hoat ong nhombai 44 b, eNhom 1 ; 2 ; 3 bai bNhom 3 ; 4 ; 5 bai cGV goi ai dien moi nhom

trnh bay bai lamGV nhan xet va sa sai neunhom nao sai sotHng dan bai tap nha:* Bai 45. Tm x : 2 25x2=0Gi y: Phan tch a thc thanhnhan t roi tm x

nhap

HS1: cau aHS2: cau bHS3: cau c

HS4: cau d(hai HS len mot lt) 1 vai HS nhan xet bai lamcua ban

Hoat ong nhomNhom 1 ; 2 ; 3 bai bNhom 3 ; 4 ; 5 bai cai dien nhom len trnh baybai lam trong bang nhom

HS ve nha hoan thanh bai giaitheo hng dan GV

= (x + 3)2b) 10x 25 x2= (x210x + 25)= (x5)2= (5 4)2

c) 8x38

1 = (2x)3(2

1 )3

= (2x 2

1 )(4x2+ 2 +4

1 )

d)25

1 x264y2= (5

1 x)2(8y)2

* Bai 44 b ; e tr 20 SGK:b) (a + b)3(a b)3= (a3+ 3a2b + 3ab2+ b3) (a33a2b + 3ab2b3)= a3+ 3a2b + 3ab2+ b3) a3+ 3a2b 3ab2+ b3= 6a2b+ 2b3= 2b(3a2+ b2)c) x3+ 9x227x + 27= 333.32. x + 3.3x2x3= (3 x)3

4.Dan dohoc sinh chuan b cho tiet hoc tiep theo: (1 phut):On lai bai, chu y van dung hang ang thc cho phu hpLam bai tap : 44a, c, d ; 45 ; 46 tr 20 21 SGK- Chuan b noi dung cho bai hoc tiep theo

IV RUT KINH NGHIEM- BO SUNG.............................................................................................................................................................................

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TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dungphan tch nao?GV goi 3 HS len bang giaiGV nhan xet ket qua bai giaicua HS khac phuc nhng sai sotcua hs

Dang 2: Tm xGV neu e toana) 2 25x2= 0

b) x2 x +4

1= 0

Cho HS tiep can e nhan dangva dung phng phap phan tchthanh nhan t e giai.Yeu cau 2HS len bang giai.

GV theo gioi sa sai neu co

Nhan xet bai giai cua HS.

Dang 3: Chng minh bieu thcchia het.

Bai tap:Tm a e a thc sauchia heta) x3+ x2 x + a chia het chox + 2b) Tm n e 7xn 3 chia het chon thc -8x5c) Tm n e 3xn + 1 2x5chiahet cho n thc -5x3Yeu cau HS nhan dang va thchien bai giai.

dung hang ang thcHS thc hien bai giai.

La dang toan tm x trc khigiai ta bien oi ve trai thanhnhan t va giaiHS thc hien bai giai.a) 2 25x2= 0 ( 0)52)(52 =+ xx

=+

=

052

052

x

x

=

=

5

25

2

x

x

b) x2 x +4

1= 0

(x - 2)2

1= 0

x =2

1

Phan tch thanh tch e chngminh.a) Lam tnh chia ta cx3+ x2 x + a=(x + 2)(x2x+1) + a 2e x3+ x2 x + a chia het chox + 2 ta phai co a 2 = 0 haya = 2b) 7xn 3 chia het cho n thc-8x5khi n 3 5 n 2c) (3xn + 1 2x5):(-5x3)

3xn + 1:(-5x3) + 25

2x

3xn + 1 2x5chia het cho nthc -5x3khi 3xn + 1chia hetcho -5x3Do o n + 1 3 n 2

= (2x + y)3e) x3+ 9x2 27x + 27= (3 x)3

Dang 2: Tm x

Bai 45 SGKa) 2 25x2= 0 ( 0)52)(52 =+ xx

=+

=

052

052

x

x

=

=

5

2

5

2

x

x

b) x2 x +4

1 = 0

(x - 2)2

1= 0

x =2

1

Dang 3: Chng minh bieuthc chia het.a) Lam tnh chia ta cx3+ x2 x + a=(x + 2)(x2x +1) + a 2e x3+ x2 x + a chia hetchox + 2 ta phai co a 2 = 0haya = 2b) 7xn 3 chia het cho nthc-8x5khi n 3 5 n

2c) (3xn + 1 2x5):(-5x3)

3xn + 1:(-5x3) + 25

2x

3xn + 1 2x5chia het chon thc -5x3khi 3xn + 1chia het cho -5x3Do o n + 1 3 n 2

3 Hoat ong 2:Cung co:

Co may cach phan tch a thcthanh nhan t

Hoat ong 2:

HS Cung co kien thc a hock nang giai toan


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?. Em co the nhom cac hang ttheo cach khac c khong ? GV lu y HS : Khi nhom cachang t ma at dau ang trcngoac th phai oi dau tat ca cachang tGV a ra v du 2 :Phan tch a thc thanh nhan t :2xy + 3z + 6y + xz GV yeu cau HS tm cac cachnhom khac nhau e phan tch ca thc thanh nhan t.GV goi HS1 len trnh bay C1vaHS2len trnh bay C2

GV cho HS nhan xet

?. Co the nhom a thc la :(2xy+3z)+(6y+xz) c khong? Taisao ?GV gii thieu : Cach lam nh cacv du tren c goi la phan tch athc thanh nhan t bang phngphap nhom hang t* oi vi mot a thc co the conhieu cach nhom nhng hang tthch hp .

HS(TB-K): Gia hai nhomlai xuat hien nhan t chungHS : at tiep (x 3)(x + y)HS : thc hien nhom theocach th hai

(x2

+ xy) + (3x 3y)

Ca lp lam vao v

HS1(TB): Trnh bay C1= (2xy + 6y) + (3z + xz)HS2(TB): Trnh bay cach 2= (2xy +xz) + ( 3z + 6y)1 vai HS nhan xetHS(K): Khong nhom cv nhom nh vay khongphan tch c a thc thanhnhan t

x23x + xy 3y= (x2+ xy) + (3x 3y)= (x2+ xy) (3x + 3y)= x(x + y) 3(x + y)= (x + y) (x 3)

b) V du 2 : Phan tch athc thanh nhan t :2xy + 3z + 6y + xz

Giai2xy + 3z + 6y + xz= (2xy + 6y) + (3z + xz)

= 2y (x + 3) + z (x + 3)= (x + 3) (2y + z)

10ph

Hoat ong 2: Ap dung:GV cho HS lam bai ?1

GV goi HS nhan xet va sa sai

GV treobang phughi e bai ?2 tr22 :Hoi : Hay neu y kien cua mnh veli giai cua cac ban Goi 2 HS len bang ong thiphan tch tiep vi cach lam cua banThao va ban Ha

Hoat ong 2:HS(TB): len bang giai

1 vai HS nhan xet va bo

sung

Ca lp quan sat e bai ?2bang phuHS tra li

2HS len bang phan tchtiepHS1: Lam tiep Thai

HS2: Lam tiep Ha

2. Ap dung?1: Tnh nhanh

15.64+25.100+36.15+60.100= (15.64 + 36.15) +

(25.100 + 60.100)= 15 (64 + 36) + 100 (25 +60)= 15 . 100 + 100. 85= 100 ( 15 + 85) = 10000?2 :An lam ung, banThai va ban Ha cha phantch het v con co the phantch tiep c.* x49x3+ x29x

= x (x39x2+ x 9)= x[(x3+ x) (9x2+ 9)]


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TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dung= x[x(x2+ 1) 9(x2+ 1)]= x (x2+ 1) (x 9)* (x 9)(x3+ x)=(x9)x(x2+ 1)

12ph

H 3 : Luyen tap cung co:

1. Phan tch a thc thanh nhan t :x2+ 6x + 9 y2Goi 1 HS len bang phan tch?. Neu ta nhom(x2+ 6x) + (9 y2) co c khong2. Yeu cau HS hoat ong nhomNa lp lam bai 48(b)Na lp lam bai 48 (c) GV kiem tra bai lam mot sonhom

GV cho HS lam bai 49 tr 22 SGK

Hng dan ve nha* Bai 50/23Gi y: at nhan t chung roi tm x

Hoat ong 3:

HS : ghi e bai vao v

1 HS len bangHoat ong nhom HS : Khong c v quatrnh phan tch tiep khongcHS : Hoat ong theo nhom ai dien nhom trnh baybai giai

HS thc hien tnh nhanh

HS hoan thanh bai giai theogi y GV

Luyen tap

1. Phan tch a thc thanhnhan t :x2+ 6x + 9 y2

= (x2+ 6x + 9) y2= (x + 3)2y2= (x + 3 + y)(x + 3 y)* Bai 48 (b, c) tr 22 :b) 3x2+ 6xy 3y23z2= 3(x2+ 2xy + y2z2)= 3 [(x + t)2z2]

= 3 (x + y + z)(xy z)c) x22xy+y2z2+ 2zt t2Ket qua :(x y + z t)(x y z+ t)* Bai 49 tr 22:Ket qua : 70 . 100 = 7000*Bai 50 tr 22:Tm x biet :x(x 2) + x 2 = 0Ket qua : x = 2 ; x = 1

4.Dan do hoc sinh chuan b cho tiet hoc tiep theo:(1 phut):Khi phan tch a thc thanh nhan t bang phng phap nhom hang t can nhom thchhpLam bai tap 47 ; 48 (a) 49 (a) ; 50 (b) tr 22 23 SGK- Chuan b noi dung cho bai hoc tiep theo.phan tch a thc thanh nhan t bang cachphoi hp nhieu phng phap

IV RUT KINH NGHIEM - BO SUNG:................................................................................................................................................................................

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Ngay soan 27/09/2009

Tiet : 13 PHAN TCH A THC THANH NHAN TBANG CACH PHOI HP NHIEU PHNG PHAP

I. MUC TIEU :

1)Kien thc : * HS biet van dung mot cach linh hoat cac phng phap phan tch a thc thanhnhan t a hoc vao viec giai loai toan phan tch a thc thanh nhan t.

2)Ky nang: * Nhan dang bai toan e ap dung phng phap phan tch thch hp.3)Thai o : * Van dung kien thc vao thc te, trung thc, hp tac trong hoat ong nhomII. CHUAN B :1.Chuan b cuagiao vien:

*Dung cu day hoc: Bai Soan SGK SBT Bang phu* Phng an day: cho hoc snh thao luan e rut ra cach giai cho bai toan.

2.Chuan b cua hoc sinh:*Dung cu hoc tap: SGK SBT, bang nhom* Kien thc on: Lam bai tap ay u, on tap cac phng phap phan tch a hoc.

III.HOAT ONG DAY HOC :1.On nh tnh hnh lp: (1phut)Kiem dien2.Kiem tra bai cu: (7phut )

HS1(TB): Giai bai tap 47 (c). Phan tch a thc thanh nhan t3x23xy 5x + 5y. Ket qua : (3x 5)(x y)Giai bai 50 (b) : Tm x biet : 5x(x 3) x + 3 = 0

Ket qua : x = 3 ; x = 1/5HS2(TB): Cha bai tap 32 b tr 6 SBTPhan tch a thc thanh nhan t : a3a2x ay + xy. Ket qua : (a x) (a2y)

3.Giangbai mi :* Gii thieu :(1phut)GV. T kiem tra bai cu. Dung may phng phap e phan tch a thc

thanh nhan t t cac bai tap tren.* Tien trnh bai day.

TG Hoat ong cua giao vien Hoat ong cua hoc sinh Noi dung15 Hoat ong 1: V du

GV a ra v du 1 SGKGV e thi gian cho HS suyngh?.Co the dung phng phap

nao e phan tch ?

?. en ay bai toan a dnglai cha ? V sao ?

?. Nh vay a dung nhngphng phap nao ?GV a ra v du 2

x2

2xy + y2

9?.Em co the dung phng phap

Hoat ong 1:HS : ghi v du vao vHS suy ngh ...

HS(TB):V ca 3 hang t eu co

5x. Nen dung phng phap atnhan t chung= 5x(x2+ 2xy + y2)HS(TB-Y):V trong ngoac lahang ang thc bnh phngcua 1 tong nen con phan tchtiep c.HS(TB): a dung phng phapat nhan t chung, tiep en laphng phap hang ang thc

HS(TB-K): V ca 4 hang t cua

1. V du :a) V du 1:Phan tch a thc thanhnhan t :5x3+ 10x2y + 5xy2

= 5x(x2+ 2xy + y2)= 5x (x + y)2


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cac phng phap : nhomhang t, dung hangang thc , at nhan tchung

10 H 3 : Cung co Luyen tap:* Bai 51 tr 24 SGK :Goi HS1 lam cau a, ba) x32x2+ xb) 2x2+ 4x + 2 2y2Goi HS2lam cau cc) 2xy x2y2+ 16

Hng dan BT nha:* Bai 55 a tr 25 SGK:Goi 1HS len bang lam cau a.Tm x biet :

x34

1 x = 0

GV cho HS khac nhan xet vasa sai

Hoat ong 3:

1 HS : oc to e baiHS1(K)lam cau a, b

HS2(TB) : lam cau c

HS(TB_K):len bang lam cau a

1 vai HS khac nhan xet vasa sai.

* Bai 51 tr 24 SGK:a) x32x2+ x= x(x22x +1) = x(x 1)2b) 2x2+ 4x + 2 2y2= 2(x2+2x + 1 y2)= 2 [(x + 1)2y2]= 2(x + 1 + y)(x + 1 y)c) 2xy x2y2+ 16= 16 (x22xy + y2)

= 16 (x y)2= (4 x + y)(4 + x y)* Bai 55 a tr 25 SGK:

a) x34

1 x = 0

x (x24

1 ) = 0

x (x +2

1 )(x 2

1 ) = 0

Vay x = 0 ; x = 21

4.Dan do hoc sinh chuan b cho tiet hoc tiep theo:(1 phut):On lai cac phng phap phan tch a thc thanh nhan tLam bai tap : 52 ; 54 ; 55 ; b, c tr 24 25 SGK bai 34 tr 7 SBT- Chuan b cho tiet hoc tiep theo phan tch a thc thanh nhan t bang cach phoi hpnhieu phng phap (tt)

IV RUT KINH NGHIEM - BO SUNG.......................................................................................................................................................................

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Ngay soan 03 / 10 / 2010Tiet 14

PHAN TCH A THC THANH NHAN TBANG CACH PHOI HP NHIEU PHNG PHAP (tt)

I. MUC TIEU :1)Kien thc : - Nam c cac dangbai phan tch a thc thanh nhan t.

- Gii thieu cho HS phng phap tach hang t, them bt hang t2)Ky nang: Ren luyen ky nang giai bai tap phan tch a thc thanh nhan t

HS giai thanh thao loai bai tap phan tch a thc thanh nhan t.3)Thai o : -Can than chnh xac trong giai toanII. CHUAN B :1)Chuan b cua giao vien:

* o dung day hoc: Bai Soan SGK SBT Bang phu* Phng an day: hoc sinh t tm li giai di s hng dan GV

2) Chuan b cua hoc sinh:* Dung cu hoc tapSGK SBT- Bang phu.* Kien thc on: on tap cac phng phap phan tch a hoc, lam bai tap ay

uIII. HOAT ONG DAY HOC :1.On nh tnh hnh lp: (1phut)Kiem dien2.Kiem tra bai cu: (6phut)

HS1(TB) : Phan tch a thc thanh nhan ta) x4+ 2x3+ x2 Ket qua x2(x + 1)2b) 5x2 10xy + 5y2 20z2 Ket qua 5(x y 2z)(x y + 2z)HS2(K): x2+ 4x + 3 Ket qua (x + 1)(x + 3)

3. Giang bai mi: * Gii thieu bai:yeu cau HS nhac lai cac phng phap phan tch a(1phut) thc thanh nhan t. GV cac phng phap o van dung nh the nao vao bai tap

o la noi dung tiet luyen tap hom nay.* Tien trnh bai day:

TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dung4 Hoat ong 1: Cung co

kien thc.Neu cac phng phap phan

tch a thc thanh nhan tc ap dung e phan tcha thc loai nay?

Cac phng phap o cvan dung nh the nao trong

cac bai tap ta giai mot sodang toan sau.

Hoat ong 1:On tap kienthc.HS(TB): Gom cac phng

phap sau:- at nhan t chung- Dung hang ang thc- Nhom hang t- Phoi hp cac phng

phap tren.Ngoai ra ngi ta con dungphng phap tach hang t


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4

5

5

Hoat ong 2: Luyen tap:* Bai 52 tr 24 SGK:Chng minh rang :(5n + 2)24 chia het cho 5vi moi so nguyen.

e chng minh mot a thcchia het cho mot so ta lamthe nao?

Goi 1 HS len bang lam

Goi 1 HS nhan xet bai lam* Bai 55 b, c tr 25:GV treo bang phu ghi ebai 55 b, c

b) (2x 1)2(x + 3)2= 0c) x2(x 3) + 12 4x = 0GV e thi gian cho HS suyngh Hoi : e tm x trong baitoan tren em lam nh thenao ? GV yeu cau 2 HS lenbang trnh bayNhan xet ket qua bai giai

cua hai hoc sinh.* Bai 56 tr 25 SGK: GV goi 1 HS oc e baicau aHoi : e tnh nhanh gia trta can phai lam nh thenao?Goi 1 HS len bang giaiNhan xet bai giai.

Hoat ong : Lam bai tap

1 HS oc e bai 52HS ca lp lam vao v

HS(K): Ta bien oi a thco thanh tch nhng a thctrong o co tha so la boi cuaso chia.HS(TB-K): Thc hien baigiai tren bang.HS(TB) nhan xet bai lam cuaban

HS oc e bai b, c bang phu

trc lp

HS : cung suy ngh va a raphng phapHS(TB): tra li phan tch athc ve trai thanh nhan t.

Hai HS len bangHS1(TB): cau b,HS2(TB): cau c

1HS oc e bai 56 a trclpHS(TB-Y):Tra li : phan tcha thc thanh nhan t va thayoi giac tr xHS len bang

* Bai 52 tr 24 SGK:

Ta co : (5n + 2)24= (5n + 2)2 22= (5n +2 2)(5n+2+2)= 5n (5n + 4)luon chia het cho 5

* Bai 55 b, c tr 25 :b) (2x 1)2(x + 3)2= 0(2x1x3)(2x1+x+3)=0

(x 4)(3x 2)x = 4 ; x =

2

3

c) x2(x 3) + 12 4x = 0x2(x 3) + 4 (3 x) = 0x2(x 3) 4 (x 3) = 0(x 3) (x2 4) = 0(x 3) (x 2) (x + 2) = 0x = 3 ; x = 2 ; x = 2

* Bai 56 tr 25 SGK :

a) x2+2

1 x +16

1

= x2. 2x . )4

1(

4

1+

2

= (x +4

1 )2thay x = 49,75

Ta co : (49,75 + 0,25)2= 502= 2500

5

Hoat ong 3: Hng danphan tch a thc thanhnhan t bang phng phapkhac:* Bai 53 tr 24 SGK:GV hng dan va giai baitoan 53 aGV a thc x23x + 2 lamot tam thc bac hai codang ax2+bx + c vi a = 1 ;

b =3 ; c = 2+ au tien ta lap tch

Hoat ong 2: phan tch athc thanh nhan t bangphng phap khac theohng dan.

HS : nghe GV hng dan

* Bai 53 tr 24 SGK:Phan tch a thc thanh nhan t :a) x23x + 2= x2x 2x + 2= (x2x) (2x 2)= x(x 1) 2(x 1)

= (x 1) (x 2)


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4

4

ac = ?+ Sau o tm xem 2 la tchcua cac cap so nguyen nao? GV ta co (-1)+(-2) = 3ung bang he so b

Ta tach 3x = x 2xVay a thc bien oi thanhx2x 2x + 2en ay GV goi 1 HS lenbang lam tiepb) x2+ 5x + 6+ Lap tch ac ... ?+ Xem 6 la tch cua cac capso nguyen nao ?+ Cap so nao co tong bang

he so 5+ Vay a thc x2+ 5x + 6c tach nh the nao ? GV goi 1 HS len bangphan tch tiep GV chot lai di dangtong quatax2+ bx + c= ax2+ b1x + b2x + cPhai co : b1+ b2= b

b1. b2= ac* Bai 55 a tr 25:a) x23x + 2GV gii thieu cach tachkhac x23x + 2= x24 3x + 6* Bai 57 a tr 25 SGK :Phan tch a thc x4+ 4 ratha soGV gi y : e lam bai nayta phai dung phng phapthem bt hang tGV : Ta thayx4= (x2)2; 4 = 22e xuat hien hang angthc bnh phng mot tong,ta can them bt 4x2e giatr ang thc khong oi x4+4=x4+4x2+4 4x2GV yeu cau HS lam tiep

HS : ac = 1.2

HS : 2 = 1.2 = (1)(2)

HS : nghe GV hng dan

HS(K):len bang lam tiep

HS : ac = 1.6 = 6HS : 6 = 1.6 = (-1)(-6)= 2.3 = (-2)(-3)

HS(TB): o la cap so 2 va 3

HS(TB-Y): x2+ 5x + 6= x2+ 2x + 3x + 6HS(TB-K): len bang phantch tiep

HS ghi vao v

HS : nghe GV gii thieu cachtach khac

HS : oc to e bai trc lp.HS : nghe GV gi y

HS (K-G):len bang lam tiep

b) x2+ 5x + 6= x2+ 2x + 3x + 6

= (x2

+ 2x) + (3x + 6)= x (x + 2) + 3(x + 2)= (x + 2) (x + 3)

* Bai 55 a tr 25 :x23x + 2= x24 3x + 6= (x24) (3x 6)= (x 2)(x + 2) 3(x 2)= (x 2)(x + 2 3)Bai 57 a tr 25 SGK :Phan tch a thcx4+ 4 ra tha soGiaix44 = x4+ 4x2+ 4 4x2

= (x2+ 2)2(2x)2= (x2+22x)(x2+2 + 2x)

5 Hoat ong 3: cung co-Hng dan hoc nha

Hoat ong 3: HS : lam bai vao v

* Bai lam them:a) 15x2 + 15xy 3x 3y


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TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dungYeu cau HS lam bai tap :phan tch a thc thanhnhan ta) 15x2+ 15xy 3x 3yb) x2+ x 6

GV nhan xet, co the choiem HSHng dan hoc nhaOn lai cac phng phapphan tch a thc thanhnhan t.Xem lai noi dung cac baitap a giai.

2 HS len bang lamHS1(K): cau a15x2+ 15xy 3x 3y=3[5x2+ 5xy x y)]= 3[5x(x + y) (x + y)]

= 3 (x + y)(5x 1)HS2(TB-K): cau bx2+ x 6= x2+ 3x 2x 6= x(x + 3) 2 (x + 3)= (x + 3) (x 2)

=3[5x2+ 5xy x y)]= 3[5x(x + y) (x + y)]= 3 (x + y)(5x 1)b) x2+ x 6= x2+ 3x 2x 6

= x(x + 3) 2 (x + 3)= (x + 3) (x 2)

4)Dan do hoc sinh chuan b cho tiet hoc tiep theo: (1 phut)Bai tap ve nha : 57 a,b ; 58 tr25 SGK ; bai 37, 38 SBT tr 7On lai quy tac chia hai luy tha cung c so

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TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dungQ : a thc thngGV gii thieu ky hieu

Q = A : B Hoac Q =B

A

GV trong bai nay, ta xet

trng hp n gian nhato la phep chia n thccho n thc

Ky hieu : Q = A : B

Hoac Q =B

A

14 Hoat ong 2: Xay dngQuy tac:GV Ta a biet, vi moi x0 ; m ; n N ; m n th :xm: xn= xmn(m > n)xm : xn= 1 (m = n)Hoi : Vay xm chia het cho

xn

khi nao ?GV yeu cau lam ?1 SGKGV goi 1HS lam mieng

Hoi : 20x5 : 12x (x 0) cophai la phep chia het ?

GV chot lai : 35 khong phaila he so nguyen ; nhng

3

5 x4 la 1 a thc nen phep

chia tren la phep chia het. GV cho HS lam tiep ?2a) Tnh 15x2y2: 5xy2Hoi : Em thc hien phepchia nay nh the nao ?

Hoi : phep chia nay co phaila phep chia het khong ?

b) 12x3: 9x2Goi 1HS thc hien phepchia

Hoat ong 2:Hieu qui tac

HS : nghe GV trnh bay

HS(TB-Y):xmchia het cho

xn

khi m nHS(TB):lam mieng :a) x3: x2= xb) 15x7: 3x2= 5x5

c) 20x5: 12x =3

5 x4

HS(TB): la mot phep chiahet v thng cua phep chiala mot a thc

HS : nghe va chot lai

HS(TB):e thc hien phepchia lay : 15 : 5 ; x2: xy2: yVay 15x2y2: 5xy2= 3xHS(TB-K): V 3x. 5xy2 =15x2y2Nh vay co a thc :Q . B = A nen la phep chiahet

HS(TB-Y): thc hien

12x3: 9x2=34 xy

2. Qui tac:Vi moi x 0 ; m ; n SGK N ; m nth :xm: xn= xmnneu m > nxm: xn= 1 neu m = n

a)Nhan xet:n thc A chia het cho n thc Bkhi moi bien cua B eu la bien cua Avi so mu khong ln so mu cua notrong A

b) Qui tac:Muon chia n thc A cho n thcB (trung hp A chia het cho B) talam nh sau :Chia he so cua n thc A cho heso cua n thc B.Chia luy tha cua tng bien trongA cho luy tha cua tng bien otrong B. Nhan cac ket qua va tm cvi nhau


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TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dungHoi : Phep chia nay co lachia het khong ?Hoi : Vay n thc A chiahet cho n thc B khi naoGV cho HS nhac lai nhan

xetHS : Muon chia n thc Acho n thc B (trng hpA chia het cho B) ta lamthe nao ?GV a bai tap len bangphu : Trong cac phep chiasau, phep chia nao la phepchia het ? Giai thch

a) 2x3y4: 5x2y4b) 15xy3: 3x2c) 4xy : 2xz

HS(Y): la phep chia het vthng la 1 a thcHS : ng tai cho tra li

HS : nhac lai nhan xet

HS(TB):neu quy tac SGKtr 26

HS(TB):Tra li :a) la phep chia hetb) La phep chia khong hetc) laphep chia khong het

5 Hoat ong 3: Ap dung:GV yeu cau HS lam bai?3Goi 2 HS len bang lam

Hoat ong 3:HS : ca lp lam vao vHS len bang lamHS1(TB): cau aHS2(K): cau b

3Ap dung:* Bai ?3 :a) 15x3y5: 5x2y3= 3xy2z

b) P = 12x4y2: (9xy2) =3

4 x3

Thay x = 3 vao PP =

3

4 . (3)3= 3

4 .(27)

P = 3612 Hoat ong 4:Luyen tap va

cung co:* Bai 60 tr 27 SGK: GV goi HS lam miengbai tap 60 tr 27GV lu y HS : Luy tha

bac chan cua hia so oinhau th bang nhau* Bai 61, 62 tr 27 SGK: GV yeu cau HS hoatong nhomGV chia lp lam 2Mot na lp lam bai 61Mot na lp lam bai 62 Goi ai dien nhom trnhbay bai lam

Hoat ong 4:

HS(TB):lam mieng bai 60

HS :hoat ong nhom

ai dien nhom trnh baybai lam

* Bai 60 tr 27 SGK:a) x10: (x)8

= x10 : x8= x2b)(x)5: (x)3= (x)2= x2

c) (-)5: (y)4= y

* Bai 61, 62 tr 27 SGK:

a) 5x2y4: 10x2y =2

1 y3

b)4

3 x3y3:

22

2

1yx =

2

3 xy

c) (xy)10: (xy)5= (xy)5= x5. y5

* Bai 62 tr 27:

15x4y3z2: 5xy2z2= 3x3yThay x = 2 ; y = 10


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TG Hoat ong cua Giao vien Hoat ong cua Hoc sinh Noi dung* Bai 42 tr 7 SBT:Tm so t nhien n e moiphep chia sau la phep chiaheta) x4: xnb) xn: x3c) 5xny3: 4x2y2d) xnyn+1: x2y5

Hng dan hoc nhaNam vng khai niem athc A chia het cho a thcB ; khi nao n thc A chiahet cho n thc B va quytac chia n thc cho n

thc

HS quan sat hnh bangphu1 HS oc to e bai2 HS len bang thc hien

HS1: cau a, bHS2: cau c, d

Ta co : 3. 23.(-10) = 240* Bai 42 tr 7 SBT:a) x4: xnx N ; n 4b) xn: x3x N ; n 3c) n N ; n 2

d) n 2n+15 n 4n N ; n 4

4.Dan do hoc sinh chuan b cho tiet hoc tiep theo: (1 phut)Bai tap ve nha : 59 (26) SGK. Bai tap 39, 40, 41, 43 tr 7 SBT- Chuan b noi dung cho tiet hoc tiep theo

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Toán 8 Tác giả: Nguyễn Việt Vy (gd) Nguồn gốc: Trường THCS Phước An, 2011 (File...

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Transcript of Toán 8 Tác giả: Nguyễn Việt Vy (gd) Nguồn gốc: Trường THCS Phước An, 2011 (File...