Point-Slope Point-Slope FormForm

What we Know so far….What we Know so far….

Slope Intercept Form

bmxy

Where m is the slope and b is the intercept

What we Know so far….What we Know so far….

Slope

12

12

xx

yy

x

y

run

risem

Where two points are given as (x1,y1) and (x2,y2)

The New Stuff… Write The New Stuff… Write equations equations

Slope-intercept form is:

bmxy

Where m is the slope and b is the y-intercept

Example: Find the equation of the line with slope -2 and y-intercept 8

y = -2x + 8Easy if I know the y-intercept… but if I don’t?

The New Stuff… Point- Slope The New Stuff… Point- Slope FormFormPoint- Slope form is:

)( 11 xxmyy Where m is the slope

and (x1,y1) is the given point that the line goes through

The New Stuff… Point- Slope The New Stuff… Point- Slope FormFormPoint- Slope form is:

)( 11 xxmyy Where does this equation come from?

mxx

yy

12

12

Using Point-Slope Form to Using Point-Slope Form to graphgraph

1 2 43

5

-1-2-3-4-5

1234

5-1-2-3-4-5

)( 11 xxmyy

)2(2

53 xy

Point is (2,3)

Slope is 2

5

Manipulate Point-Slope Manipulate Point-Slope Form to Slope-Intercept Form to Slope-Intercept

formform)2(

2

53 xy

Simplify5

2

53 xy

22

5 xy

Using Point-Slope Form to Using Point-Slope Form to graphgraph

1 2 43

5

-1-2-3-4-5

1234

5-1-2-3-4-5

)( 11 xxmyy

)4(23 xy

Point is (4,-3)

Slope is 1

2

Manipulate Point-Slope Manipulate Point-Slope Form to Slope-Intercept Form to Slope-Intercept

formform

823 xy

52 xy

)4(23 xy

Your turnYour turn

)1(3

11 xy

)3(2

52 xy

)1(4

13 xy

HomeworkHomework

Pg. 304 #2 to 8 evenPg. 304 #2 to 8 even

Write slope and pointWrite slope and point

Plot graphPlot graph

Write equation in slope Write equation in slope intercept formintercept form