Warm up

2

1

2

1

Write the equation of the line passing through the given point with the given slope. Then graph the line.

1. (-4, -3), m =

2. (8, 2), m =

answers

1. Y= ½ x – 1

2. Y= -½ x + 6

How do we use Two Points to Write an Equation?

Step 1: Find the slope.Step 2: Use one of the

points and your slope to solve for b.

Step 3: Write your equation in slope-intercept form using slope and y-intercept

Example

Write an equation for the line through these points. (-1,-5) and (-2, 3).

3 ( 5)

2 ( 1)m

8

1m

83 ( 2)

1b 3 16 b

3 16 16 16 b

13b 813

1y x

Your Turn:

Write an equation for the line through these points.

(1, 3) and (-1, -1)

(-1, 6) and (7, -10)

(10, -1) and (4, 2)

(-14, -2) and (7, 7)4

2

1 xy

47

3 xy

12 xy

42 xy

Write an equation of the line that has each pair of intercepts

x-intercept: (-3,0), y-intercept: (0,6)

)3(0

06

m 2m

b )3(20 b6

62 xy

Your Turn:

Write an equation of the line that has an x-intercept of (2,0) and a y-intercept of (0,-5).

20

05

m2

5m

b )0(2

55 b 5

52

5 xy

Part 2: How do write an equation using a table?

Step 1: Find the rate of change. (change in Y over change in X)

Step 2: Use either point and your slope to solve for b.

Step 3: Write your equation in slope-intercept form using slope and y-intercept

X Y

-1 4

3 6

5 7

11 10

2

9

2

1 xy

Your Turn:

Write in slope-intercept form.

X Y

-11 -7

-1 -3

4 -1

19 55

13

5

2 xy

Review Key Concepts

Slope-intercept Form• Y = mx + b

• Ex. Y=-½x + 5

Standard Form

• Ax + By = C

• Ex. 2x + 3y= 5

Summary:

Name the steps for writing an equation from two points?