1. Do Now 2/6/12
In your notebook, define the word INTERCEPT in your own words. Then graph the equation below by making a table.
2x + 3y = 12. x -6 -3 3 6 y 8 4 2

2. Objective
SWBAT graph a linear equation using intercepts

3. Section 8.3 “Using Intercepts”
x-intercept-
the x-coordinate of the point where the line crosses the x-axis
To find the x-intercept, solve for ‘x’ when ‘y = 0.’
Find the x-intercept of the graph 2x + 3y = 12.
2x + 3y = 12
2x + 3(0)= 12
2x = 12
x = 6

4. Find the y-intercept of the graph 2x + 3y = 12.
the y-coordinate of the point where the line crosses the y-axis
To find the y-intercept, solve for ‘y’ when ‘x = 0.’
Find the y-intercept of the graph 2x + 3y = 12.
2x + 3y = 12
2(0)+ 3y= 12
3y = 12
y = 4

5. Graph the equation 2x + 3y = 12.
Graph an Equation Using Intercepts
Graph the equation 2x + 3y = 12.
y-axis
Plot the two intercepts as points and then connect the points using a line. 10 8 6 4
The x-intercept = 6
(0,4) 2
(6,0)
(6,0)
-12
-10 -8 -6 -4 -2 2 4 6 8 10 12
x-axis
The y-intercept = 4 -2
(0,4) -4 -6
Remember this? -8 x -6 -3 3 6 y 8 4 2
-10

6. Use Intercepts to Graph an Equation
Graph the equation x + 2y = 4.
Find the x-intercept
Find the y-intercept
x + 2y = 4
x + 2y = 4
x + 2(0) = 4
0 + 2y = 4
x = 
x-intercept 4
y = 
y-intercept 2
Plot points. The x-intercept is 4, so plot the point (4, 0). The y- intercept is 2, so plot the point (0, 2). Draw a line through the points.

7. Use Intercepts to Graph an Equation
Graph the equation 6x + 7y = 42.
Find the x-intercept
Find the y-intercept
6x + 7y = 42
6x + 7y = 42
6x + 7(0)= 42
6(0) + 7y = 42
x = 
x-intercept 7
y = 
y-intercept 6
Plot points. The x-intercept is 7, so plot the point (7, 0). The y- intercept is 6, so plot the point (0, 6). Draw a line through the points.

8. Use a Graph to Find Intercepts
The graph crosses the x-axis at (2, 0). The x-intercept is 2.
The graph crosses the y-axis at (0, – 1). The y-intercept is – 1.

9. Use a Graph to Find Intercepts
The graph crosses the x-axis at (–4, 0). The x-intercept is –4.
The graph crosses the y-axis at (0, 2). The y-intercept is 2.

10. Problem Solving Using Linear Equations
You are working at a local park and are in charge of renting skateboards and bikes. You rent bikes for $8.00 a day and skateboards for $4.00 a day. At the end of the day you have made a profit of $1200.
Using the graph, make a table of values to show the different combinations of rentals that could have resulted in a $1200 profit.
Write an algebraic equation to represent the situation. Use ‘x’ for skateboards and ‘y’ for bikes.
4x + 8y = 1200
150
bikes
100 50 50
100
150
200
250
300
skateboards