1. Lesson 15
Linear Equations
The Slope Formula

2. Warm-Up Draw a line through each pair of points. Draw a slope
triangle and find the slope.
(1, 3) and (5, 4)
(−2, 6) and (1, 0)

3. Target: Find the slope of a line using the slope formula.

6. The Slope Formula
The formula for the slope of a line that goes through a point with coordinates (x1, y1) and another point with coordinates (x2, y2) is:

7. Example 1ab Use the slope formula to find the slope of each line that
passes through the given points.
(3, 2) and (8, 5)
(1, −1) and (3, −5)

8. Example 1c Use the slope formula to find the slope of each line that
passes through the given points.
(6, −1) and (6, 4)
Undefined Slope

9. Exit Problems Find the slope of each line that passes through the
given points.
(4, 0) and (7, 9)
(9, 2) and (6, 4)
(4, −1) and (4, 3)

10. Communication Prompt You can find slope from:
A table by finding rate of change.
A graph using a slope triangle.
The slope formula.
Which way do you prefer to find slope? Why?