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

Objective SWBAT graph a linear equation using intercepts

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

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

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

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.

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.

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.

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.

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