1. Objective
Find slope by using the slope formula.

3. Example 1: Finding Slope by Using the Slope Formula
Find the slope of the line that contains (2, 5) and (8, 1).
Use the slope formula.
Substitute (2, 5) for (x1, y1) and (8, 1) for (x2, y2).
Simplify.
The slope of the line that contains (2, 5) and (8, 1) is

4. Check It Out! Example 1a
Find the slope of the line that contains (–2, –2) and (7, –2).
Use the slope formula.
Substitute (–2, –2) for (x1, y1) and (7, –2) for (x2, y2).
Simplify.
= 0
The slope of the line that contains (–2, –2) and (7, –2) is 0.

5. Check It Out! Example 1b
Find the slope of the line that contains (5, –7) and (6, –4).
Use the slope formula.
Substitute (5, –7) for (x1, y1) and (6, –4) for (x2, y2).
Simplify.
= 3
The slope of the line that contains (5, –7) and (6, –4) is 3.

6. The graph shows a linear relationship. Find the slope.
Check It Out! Example 2a
The graph shows a linear relationship. Find the slope.
Let (2, 2) be (x1, y1) and (4, 3) be (x2, y2).
Use the slope formula.
Substitute (2, 2) for (x1, y1) and (4, 3) for (x2, y2).
Simplify.

7. The graph shows a linear relationship. Find the slope.
Check It Out! Example 2b
The graph shows a linear relationship. Find the slope.
Let (–2, 4) be (x1, y1) and (0, –2) be (x2, y2).
Use the slope formula.
Substitute (–2, 4) for (x1, y1) and (0, –2) for (x2, y2).
Simplify.

8. The table shows a linear relationship. Find the slope.
Check It Out! Example 2d
The table shows a linear relationship. Find the slope.
Step 1 Choose any two points from the table. Let (0, 0) be (x1, y1) and (–2, 3) be (x2, y2).
Step 2 Use the slope formula.
Use the slope formula.
Substitute (0, 0) for (x1, y1) and (–2, 3) for (x2, y2).
Simplify

9. Example 3: Application
The graph shows the average electricity costs (in dollars) for operating a refrigerator for several months. Find the slope of the line. Then tell what the slope represents.
Step 1 Use the slope formula.

10. Example 4: Finding Slope from an Equation
Find the slope of the line described by 4x – 2y = 16.
Step 1 Find the x-intercept.
Step 2 Find the y-intercept.
4x – 2y = 16
4x – 2y = 16
4x – 2(0) = 16
Let y = 0.
4(0) – 2y = 16
Let x = 0.
4x = 16
x = 4
–2y = 16
y = –8
Step 3 The line contains (4, 0) and (0, –8). Use the slope formula.