Limit Rules -...

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Limit Rules Useful rules for finding limits:

Transcript of Limit Rules -...

Page 1: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit RulesUseful rules for finding limits:

In the following rules assume k = constant

limx→c

k = k

limx→c

kf(x) = k limx→c

f(x)

limx→c

f(x)± g(x) = limx→c

f(x)± limx→c

g(x)

limx→c

f(x) · g(x) = limx→c

f(x) · limx→c

g(x)

limx→c

f(x)

g(x)=

limx→c f(x)

limx→c g(x)( 6=0)

limx→c

[f(x)n] =[limx→c

f(x)]n

limx→c

P(x) = P(c) , P(x) is continuous around c, just plug-in

Page 2: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit RulesUseful rules for finding limits:In the following rules assume k = constant

limx→c

k = k

limx→c

kf(x) = k limx→c

f(x)

limx→c

f(x)± g(x) = limx→c

f(x)± limx→c

g(x)

limx→c

f(x) · g(x) = limx→c

f(x) · limx→c

g(x)

limx→c

f(x)

g(x)=

limx→c f(x)

limx→c g(x)( 6=0)

limx→c

[f(x)n] =[limx→c

f(x)]n

limx→c

P(x) = P(c) , P(x) is continuous around c, just plug-in

Page 3: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit RulesUseful rules for finding limits:In the following rules assume k = constant

limx→c

k = k

limx→c

kf(x) = k limx→c

f(x)

limx→c

f(x)± g(x) = limx→c

f(x)± limx→c

g(x)

limx→c

f(x) · g(x) = limx→c

f(x) · limx→c

g(x)

limx→c

f(x)

g(x)=

limx→c f(x)

limx→c g(x)( 6=0)

limx→c

[f(x)n] =[limx→c

f(x)]n

limx→c

P(x) = P(c) , P(x) is continuous around c, just plug-in

Page 4: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit RulesUseful rules for finding limits:In the following rules assume k = constant

limx→c

k = k

limx→c

kf(x) = k limx→c

f(x)

limx→c

f(x)± g(x) = limx→c

f(x)± limx→c

g(x)

limx→c

f(x) · g(x) = limx→c

f(x) · limx→c

g(x)

limx→c

f(x)

g(x)=

limx→c f(x)

limx→c g(x)( 6=0)

limx→c

[f(x)n] =[limx→c

f(x)]n

limx→c

P(x) = P(c) , P(x) is continuous around c, just plug-in

Page 5: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit RulesUseful rules for finding limits:In the following rules assume k = constant

limx→c

k = k

limx→c

kf(x) = k limx→c

f(x)

limx→c

f(x)± g(x) = limx→c

f(x)± limx→c

g(x)

limx→c

f(x) · g(x) = limx→c

f(x) · limx→c

g(x)

limx→c

f(x)

g(x)=

limx→c f(x)

limx→c g(x)( 6=0)

limx→c

[f(x)n] =[limx→c

f(x)]n

limx→c

P(x) = P(c) , P(x) is continuous around c, just plug-in

Page 6: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit RulesUseful rules for finding limits:In the following rules assume k = constant

limx→c

k = k

limx→c

kf(x) = k limx→c

f(x)

limx→c

f(x)± g(x) = limx→c

f(x)± limx→c

g(x)

limx→c

f(x) · g(x) = limx→c

f(x) · limx→c

g(x)

limx→c

f(x)

g(x)=

limx→c f(x)

limx→c g(x)( 6=0)

limx→c

[f(x)n] =[limx→c

f(x)]n

limx→c

P(x) = P(c) , P(x) is continuous around c, just plug-in

Page 7: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit RulesUseful rules for finding limits:In the following rules assume k = constant

limx→c

k = k

limx→c

kf(x) = k limx→c

f(x)

limx→c

f(x)± g(x) = limx→c

f(x)± limx→c

g(x)

limx→c

f(x) · g(x) = limx→c

f(x) · limx→c

g(x)

limx→c

f(x)

g(x)=

limx→c f(x)

limx→c g(x)( 6=0)

limx→c

[f(x)n] =[limx→c

f(x)]n

limx→c

P(x) = P(c) , P(x) is continuous around c, just plug-in

Page 8: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit RulesUseful rules for finding limits:In the following rules assume k = constant

limx→c

k = k

limx→c

kf(x) = k limx→c

f(x)

limx→c

f(x)± g(x) = limx→c

f(x)± limx→c

g(x)

limx→c

f(x) · g(x) = limx→c

f(x) · limx→c

g(x)

limx→c

f(x)

g(x)=

limx→c f(x)

limx→c g(x)( 6=0)

limx→c

[f(x)n] =[limx→c

f(x)]n

limx→c

P(x) = P(c) , P(x) is continuous around c, just plug-in

Page 9: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit RulesUseful rules for finding limits:In the following rules assume k = constant

limx→c

k = k

limx→c

kf(x) = k limx→c

f(x)

limx→c

f(x)± g(x) = limx→c

f(x)± limx→c

g(x)

limx→c

f(x) · g(x) = limx→c

f(x) · limx→c

g(x)

limx→c

f(x)

g(x)=

limx→c f(x)

limx→c g(x)( 6=0)

limx→c

[f(x)n] =[limx→c

f(x)]n

limx→c

P(x) = P(c) , P(x) is continuous around c, just plug-in

Page 10: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) = 3 + 3 = 6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 11: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) = 3 + 3 = 6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 12: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) = 3 + 3 = 6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 13: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) = 3 + 3 = 6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 14: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) = 3 + 3 = 6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 15: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form.

When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) = 3 + 3 = 6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 16: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) = 3 + 3 = 6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 17: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3=

limx→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) = 3 + 3 = 6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 18: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)=

limx→3

(x + 3) = 3 + 3 = 6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 19: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) =

3 + 3 = 6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 20: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) = 3 + 3 =

6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 21: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) = 3 + 3 = 6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 22: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) = 3 + 3 = 6

Indeterminant does not mean the limit does not exist.

It just means that the method you tried did not tell you anythingand you need to try another method.

Page 23: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→3

x2 − 9

x− 3=?

first try “limit of ratio = ratio of limits rule”,

limx→3

x2 − 9

x− 3=

limx→3 x2 − 9

limx→3 x− 3=

0

0

00 is called an indeterminant form. When you reach an indeterminant formyou need to try someting else.

limx→3

x2 − 9

x− 3= lim

x→3

(x− 3)(x + 3)

(x− 3)= lim

x→3(x + 3) = 3 + 3 = 6

Indeterminant does not mean the limit does not exist.It just means that the method you tried did not tell you anythingand you need to try another method.

Page 24: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant forms

I when taking limits, 00 , ∞

∞ and∞ · 0 are called indeterminantforms.

I indeterminant form means that the method you used to findthe limit led you to a point where you cannot make anyconclusions about the limit.

I when you reach an indeterminant form, you must try anothermethod to determine the limit. This usually means to first usean algebra trick and then continue finding the limit.

I indeterminant does not mean that the limit cannot bedetermined. It only means that the method you used did notwork. You must try another method to determine the limit. Insome cases this could just mean using the table method.

Page 25: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant forms

I when taking limits, 00 , ∞

∞ and∞ · 0 are called indeterminantforms.

I indeterminant form means that the method you used to findthe limit led you to a point where you cannot make anyconclusions about the limit.

I when you reach an indeterminant form, you must try anothermethod to determine the limit. This usually means to first usean algebra trick and then continue finding the limit.

I indeterminant does not mean that the limit cannot bedetermined. It only means that the method you used did notwork. You must try another method to determine the limit. Insome cases this could just mean using the table method.

Page 26: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant forms

I when taking limits, 00 , ∞

∞ and∞ · 0 are called indeterminantforms.

I indeterminant form means that the method you used to findthe limit led you to a point where you cannot make anyconclusions about the limit.

I when you reach an indeterminant form, you must try anothermethod to determine the limit. This usually means to first usean algebra trick and then continue finding the limit.

I indeterminant does not mean that the limit cannot bedetermined. It only means that the method you used did notwork. You must try another method to determine the limit. Insome cases this could just mean using the table method.

Page 27: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant forms

I when taking limits, 00 , ∞

∞ and∞ · 0 are called indeterminantforms.

I indeterminant form means that the method you used to findthe limit led you to a point where you cannot make anyconclusions about the limit.

I when you reach an indeterminant form, you must try anothermethod to determine the limit. This usually means to first usean algebra trick and then continue finding the limit.

I indeterminant does not mean that the limit cannot bedetermined. It only means that the method you used did notwork. You must try another method to determine the limit. Insome cases this could just mean using the table method.

Page 28: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→4

x− 4√

x− 2=?

First try “limit of ratio = ratio of limits rule” and will again get 00

an indeterminant form. Try an algebra trick:

limx→4

x− 4√

x− 2= lim

x→4

(√

x)2 − 22

(√

x− 2)(1)

= limx→4

(√

x− 2)(√

x + 2)

(√

x− 2)(2)

= limx→4

(√

x + 2) (3)

= (√

4 + 2) = 2 + 2 = 4 (4)

Page 29: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→4

x− 4√

x− 2=?

First try “limit of ratio = ratio of limits rule”

and will again get 00

an indeterminant form. Try an algebra trick:

limx→4

x− 4√

x− 2= lim

x→4

(√

x)2 − 22

(√

x− 2)(1)

= limx→4

(√

x− 2)(√

x + 2)

(√

x− 2)(2)

= limx→4

(√

x + 2) (3)

= (√

4 + 2) = 2 + 2 = 4 (4)

Page 30: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→4

x− 4√

x− 2=?

First try “limit of ratio = ratio of limits rule” and will again get 00

an indeterminant form. Try an algebra trick:

limx→4

x− 4√

x− 2= lim

x→4

(√

x)2 − 22

(√

x− 2)(1)

= limx→4

(√

x− 2)(√

x + 2)

(√

x− 2)(2)

= limx→4

(√

x + 2) (3)

= (√

4 + 2) = 2 + 2 = 4 (4)

Page 31: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→4

x− 4√

x− 2=?

First try “limit of ratio = ratio of limits rule” and will again get 00

an indeterminant form.

Try an algebra trick:

limx→4

x− 4√

x− 2= lim

x→4

(√

x)2 − 22

(√

x− 2)(1)

= limx→4

(√

x− 2)(√

x + 2)

(√

x− 2)(2)

= limx→4

(√

x + 2) (3)

= (√

4 + 2) = 2 + 2 = 4 (4)

Page 32: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→4

x− 4√

x− 2=?

First try “limit of ratio = ratio of limits rule” and will again get 00

an indeterminant form. Try an algebra trick:

limx→4

x− 4√

x− 2= lim

x→4

(√

x)2 − 22

(√

x− 2)(1)

= limx→4

(√

x− 2)(√

x + 2)

(√

x− 2)(2)

= limx→4

(√

x + 2) (3)

= (√

4 + 2) = 2 + 2 = 4 (4)

Page 33: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesexample

limx→4

x− 4√

x− 2=?

First try “limit of ratio = ratio of limits rule” and will again get 00

an indeterminant form. Try an algebra trick:

limx→4

x− 4√

x− 2= lim

x→4

(√

x)2 − 22

(√

x− 2)(1)

= limx→4

(√

x− 2)(√

x + 2)

(√

x− 2)(2)

= limx→4

(√

x + 2) (3)

= (√

4 + 2) = 2 + 2 = 4 (4)

Page 34: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulessame example, new trick

limx→4

x− 4√

x− 2= lim

x→4

x− 4

(√

x− 2)·(√

x + 2)

(√

x + 2)(5)

= limx→4

(x− 4)(√

x + 2)

(√

x− 2)(√

x + 2)(6)

= limx→4

(x− 4)(√

x + 2)

(x− 4)(7)

= limx→4

(√

x + 2) (8)

= (√

4 + 2) = 2 + 2 = 4 (9)

Page 35: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form 0

0

There are three cases for limx→cf(x)g(x) = 0

0

limx→c

f(x)

g(x)=

0 top goes to 0 faster than bottomconstant 6= 0 top and bottom go to 0 at same rate∞ bottom goes to zero faster than top

Page 36: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form 0

0

There are three cases for limx→cf(x)g(x) = 0

0

limx→c

f(x)

g(x)=

0 top goes to 0 faster than bottom

constant 6= 0 top and bottom go to 0 at same rate∞ bottom goes to zero faster than top

Page 37: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form 0

0

There are three cases for limx→cf(x)g(x) = 0

0

limx→c

f(x)

g(x)=

0 top goes to 0 faster than bottomconstant 6= 0 top and bottom go to 0 at same rate

∞ bottom goes to zero faster than top

Page 38: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form 0

0

There are three cases for limx→cf(x)g(x) = 0

0

limx→c

f(x)

g(x)=

0 top goes to 0 faster than bottomconstant 6= 0 top and bottom go to 0 at same rate∞ bottom goes to zero faster than top

Page 39: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form ∞

There are three cases for limx→c f(x) = ∞∞

limx→c

f(x)

g(x)=

∞ top goes to∞ faster than bottomconstant 6= 0 top and bottom go to∞ at same rate0 bottom goes to∞ faster than top

Page 40: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form ∞

There are three cases for limx→c f(x) = ∞∞

limx→c

f(x)

g(x)=

∞ top goes to∞ faster than bottomconstant 6= 0 top and bottom go to∞ at same rate0 bottom goes to∞ faster than top

Page 41: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form ∞

There are three cases for limx→c f(x) = ∞∞

limx→c

f(x)

g(x)=

∞ top goes to∞ faster than bottom

constant 6= 0 top and bottom go to∞ at same rate0 bottom goes to∞ faster than top

Page 42: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form ∞

There are three cases for limx→c f(x) = ∞∞

limx→c

f(x)

g(x)=

∞ top goes to∞ faster than bottomconstant 6= 0 top and bottom go to∞ at same rate

0 bottom goes to∞ faster than top

Page 43: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form ∞

There are three cases for limx→c f(x) = ∞∞

limx→c

f(x)

g(x)=

∞ top goes to∞ faster than bottomconstant 6= 0 top and bottom go to∞ at same rate0 bottom goes to∞ faster than top

Page 44: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form ∞

∞ , 00

Exercise: to demonstrate the preveous six results evaluate thefollowing six limits by using the table method for each:

1. limx→∞xx2

2. limx→∞x2

x

3. limx→∞x2

x2

4. limx→0xx2

5. limx→0x2

x

6. limx→0x2

x2

Use powers of 10 for x

Page 45: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form ∞

∞ , 00

Exercise: to demonstrate the preveous six results evaluate thefollowing six limits by using the table method for each:

1. limx→∞xx2

2. limx→∞x2

x

3. limx→∞x2

x2

4. limx→0xx2

5. limx→0x2

x

6. limx→0x2

x2

Use powers of 10 for x

Page 46: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form ∞

∞ , 00

Exercise: to demonstrate the preveous six results evaluate thefollowing six limits by using the table method for each:

1. limx→∞xx2

2. limx→∞x2

x

3. limx→∞x2

x2

4. limx→0xx2

5. limx→0x2

x

6. limx→0x2

x2

Use powers of 10 for x

Page 47: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form ∞

∞ , 00

Exercise: to demonstrate the preveous six results evaluate thefollowing six limits by using the table method for each:

1. limx→∞xx2

2. limx→∞x2

x

3. limx→∞x2

x2

4. limx→0xx2

5. limx→0x2

x

6. limx→0x2

x2

Use powers of 10 for x

Page 48: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form ∞

∞ , 00

Exercise: to demonstrate the preveous six results evaluate thefollowing six limits by using the table method for each:

1. limx→∞xx2

2. limx→∞x2

x

3. limx→∞x2

x2

4. limx→0xx2

5. limx→0x2

x

6. limx→0x2

x2

Use powers of 10 for x

Page 49: Limit Rules - homepages.math.uic.eduhomepages.math.uic.edu/~rmlowman/math165/LectureNotes/L5-W2L2r… · Limit Rules example lim x!3 x2 9 x 3 =? rst try \limit of ratio = ratio of

Limit Rulesindeterminant form ∞

∞ , 00

Exercise: to demonstrate the preveous six results evaluate thefollowing six limits by using the table method for each:

1. limx→∞xx2

2. limx→∞x2

x

3. limx→∞x2

x2

4. limx→0xx2

5. limx→0x2

x

6. limx→0x2

x2

Use powers of 10 for x