1. Today’s objective: To graph linear equations in slope intercept form
Lesson 6-2-(part 1) Writing Equations in Slope-Intercept Form & Graphing Lines (page 291)
Today’s objective: To graph linear equations in slope intercept form

2. Real-World Connection
This skill can be used for relating total earnings to sales. (See Example 5.)

3. Vocabulary Linear equation – an equation whose graph is a line.
y-intercept – the y-coordinate of the point where a line crosses the y-axis.
Slope-intercept form –
y = mx + b
where m = slope and b = y-intercept.

4. Slope-Intercept Form What are the slope and y-intercept of y = 2x – 3?
mx + b =
2x – 3
Use the Slope-Intercept form.
The slope is 2; the y-intercept is –3.
6-2

5. Example 1, page 292 Find the slope and y-intercept of each equation.
A) y = -2x + 1
B) y = (7/6)x – 3/4
C) y = -(4/5)x

6. Graphing Lines using the Slope and y-intercept
Plot the y-intercept.
From this point, use the slope and rise/run to plot a second point.
Repeat step 2 to get a third point.
Draw a line through the three points.

7. Slope-Intercept Form Graph y = x – 2. Step 21 3
Step 2
The slope is . Use slope to plot a second point. 1 3
Step 3
Draw a line through
the two points.
Step 1
The y-intercept is –2.
So plot a point at (0,–2).
6-2

8. Example 4: GRAPH
y= 3x y = 3/2 x - 2 y x 10
-10 y x 10
-10

9. y = -2x + 1 y = -2/3 x + 3 y x 10
-10 y x 10
-10

10. y = -2x y – 9x = 1/2 y x 10
-10 y x 10
-10

11. y – 2 = -3x y x 10
-10 y x 10
-10

12. Slope-Intercept Form
The base pay for a used car salesperson is $300 per week.
The salesperson also earns 15% commission on sales made. The equation t = s relates total earnings t to sales s. Graph the equations.
Step 1  Identify the slope and y-intercept.
t = s
t = 0.15s + 300  Rewrite the equation in slope intercept form.
slope y-intercept
6-2

13. Slope-Intercept Form
(continued)
Step 2  Plot two points. First plot a point at the y-intercept. Then use the slope to plot a second point. The slope is 0.15, which equals Plot a second point 15 units above and 100 units to the right of the y-intercept. 15
100
Step 3  Draw a line through the points.
6-2

14. Example 5, page 293
Suppose the base pay of the delivery person is $150 and his commission on each sale is 30%. The equation relating his total earnings t to sales s is
t = s. Graph the equation. y x 2

15. Summary
What did you learn today?

16. Summary What is the y-intercept?
What is the slope intercept form of an equation?
What does m represent? What does b represent?
How can we graph a line using the slope and y-intercept?

17. ASSIGNMENT
page 294
#1-9 all
28-40 all
odd