1. Section 8.3 Part 2
Slope and y-intercept
pages

2. Using Slope to Graph Linear Equations
Here is the graph of y = - ½ x + 3
The slope of the line is - 2/4, or ½
The line crosses the y-axis at (0,3). We call this point the y-intercept.

3. The graph can be described by the equation
y = - ½ x + 3
slope
y- intercept

4. Key Concepts Slope-intercept form
The equation y = mx + b is the slope-intercept form.
In this form, m is the slope.
b is the y–intercept.
Slope–intercept form can be used to graph equations.

5. Examples
A ramp slopes from a warehouse door down to the street. The function y = 1/5 x + 4 models the ramp, where x is the horizontal distance in feet from the bottom of the door and y is the height in feet above the street. Graph the equation.

6. y = - 1/5 x + 4 (1) Since the y- intercept is 4, graph (0,4).
(2) Since the slope is -1/5 , or -1/5,
--move 1 unit down from (0,4).
--then move 5 units right to graph the second point.
(3) Draw a line through the points

7. Check Understanding
Graph y = 2x -3
y–intercept:
slope:

8. Check Understanding
Graph y = -x + 4
y–intercept:
slope:

9. Homework
Pages 414 – 416,
#s 11-19, 30-40,46-51