Chapter 5:Write the equation of a line

Given Two Points

Lesson 5.3: Writing an equation given two points -Mathematically

Step 1: Substitute values into the slope formula to find the m.

1 1my xy x

Step 2: Select one of the point to substitute into point-slope formula and solve for y.

2 1

2 1-

-x

ym

x

y

Lesson 5.3: Writing an equation given two points

1 1( , )x y2 2( , )x y

2 1

2 1

x

ym

x

y

-3

4

m

1 -1

m2

2m1

Write the equation of the line that pass through these points (-1 , -3) & (1 , 1).

Step 1: Substitute values into slope formula to find the m.

Lesson 5.3: Writing an equation given two points -Mathematically

Step 2: Select a point to substitute into point-slope formula

2x12 1y x

1

2m -3-1, & 1,1

1 1my xy x y x 21

1y 21

Lesson 5.3: Writing an equation given two points

1 1( , )x y2 2( , )x y

2 1

2 1

x

ym

x

y

3

- 2

m

3 -3

m6

1-3

m1

Write the equation of the line that pass through these points (-3 , 3) & (3 , 1).

Step 1: Substitute values into slope formula to find the m.

Lesson 5.3: Writing an equation given two points -Mathematically

Step 2: Select a point to substitute into point-slope formula

1-3x

1

32

1-y x

3

1-3

m -3, 3 & 3,1

1 1my xy x

y x 1-3

1

1y 11

Lesson 5.3: Writing an equation given two points -Graphically

Step 1: Plot both points

Step 2: Determine the slope (m).

Step 3: Find the y-intercept (b).

y bmx Step 4: Write equation in slope-intercept form

1 1 2 2, & ,x y x y

Lesson 5.3: Writing an equation given two points -Graphically

( 2 , 4 ) & (2 , 2 )

1

2m

(0, 3)b

Step 1: Plot the points

x

y

Step 2: Determine the slope (m).

4

2

2 4

-2

-4

-2-4Step 3: Find the y-intercept

Step 4: Write equation in slope-intercept form

13

2y x

Lesson 5.3: Writing an equation given two points -Graphically

( 1 , 3 ) & (1,1 )

2m

(0, 1)b

Step 1: Plot the points

x

y

Step 2: Determine the slope (m).

4

2

2 4

-2

-4

-2-4Step 3: Find the y-intercept

Step 4: Write equation in slope-intercept form

2 1y x