1. Algebra 1
Section 6.3

2. Slope-Intercept Form
The slope-intercept form of a linear equation is y = mx + b.
m is the slope of the line.
b is the y-coordinate of the y- intercept, (0, b).

3. Example 1 To write 3x + 2y = 6 in slope- intercept form, solve for y.
2y = 6 – 3x 3 2
y = 3 – x 3 2
y = x + 3

4. Example 1 3 y = - x + 3 2 3 The slope is - . 2
The y-intercept is (0, 3).

5. Forms of Linear Equations
Standard form: 3x + 2y = 6
Slope-intercept form:
Function form: 3 2
y = x + 3 3 2
f(x) = x + 3

6. Slope-Intercept Form
To change a linear equation to slope-intercept form:
Solve the linear equation for y.
Arrange terms on the right side with the variable term first.

7. Slope-Intercept Form
The slope-intercept form of a line can be used to quickly graph the line.
First, plot the y-intercept.
Then, use the slope to plot one or more other points.

8. Example 2
Graph y = ½x + 4.
The y-intercept is (0, 4). y x

9. Example 2 The slope is ½. Move up 1 and to the right 2.
Another point could be added.
Draw a line through the points. y x

10. Example 3 Write 2x + 3y = -3 as a linear function. 3y = -2x - 3 2
f(x) = x – 1

11. Example 4 Write y = 3 in slope-intercept form. y = 0x + 3
The slope is 0.
The y-intercept is 3.

12. Example 4
y = 0x + 3 y x

13. This is a constant function.
Example 4
f(x) = 3
This is a constant function. x

14. Example 5 Let n = the number of pages. C(n) = 1.25n + 25
For a 23-page album:
C(23) = 1.25(23) + 25 = $53.75

15. Homework: pp