1. Writing Linear Equations When Given Two Points on the Line
Teacher Twins©2014

2. Warm Up
Write an equation in slope intercept form when given the slope and a point.
y = 8
y = -4/7x + 5
y = 8x + 20
x = 7

3. Writing Linear Equations When Given Two Points on the Line

4. What two things do I need to write an equation of a line?
Slope
and
y intercept

5. Write an equation of a line when given two points.
(1, -4), (-2, 11)
Find the slope
-2 - 1 15 -3 =
= -5
Use the slope and pick one of the points.
m = -5 and (1, -4)

6. Substitute into y = mx + b -4 = -5(1) + b b = 1
Use the slope and pick one of the points.
m = -5 and (1, -4)
Substitute into y = mx + b
-4 = -5(1) + b b = 1
Slope = -5 and the y intercept is 1.
The equation is y = -5x + 1

7. Graph the two ordered pairs and draw a line. Notice the y intercept.
The y intercept is 1, just like we found when we used the slope intercept equation.

8. y = 𝟏 𝟐 x - 2 Write an equation of a line when given two points.
(-2, -3), (4, 0)
y = 𝟏 𝟐 x - 2

9. Practice y = -x + 6 y = 1/3x - 1 x = 4
Write an equation of a line when given two points.
(-2, 8), (5, 1)
(0, -1), (6, 1)
(4, -1), (4, 9)
y = -x + 6
y = 1/3x - 1
x = 4

10. Closure
Write an equation in slope intercept form that goes through
y = 2x - 5