In this lesson we will explore x and y intercepts of linear equations

Graph 2x – 3y = 12 First, solve for y – 3y = -2x y = 2x – 4 3

Begin the graph at –4 on the y-axis (the y-intercept)

Count up 2 then right 3 The slope is 2 3 Where does this line cross the x-axis?

Type this equation under y= in the calculator View the table What are the x and y intercepts?

When the x-coordinate is 0, the point lies on the y-axis. This point is called the y-intercept. The y-intercept for this equation is -4

When the y-coordinate is 0, the point lies on the x-axis. This point is called the x-intercept. The x-intercept for this equation is 6

We can find the x and y intercepts another way xy 0 0 2x – 3y = 12

Replace the y in the equation with zero and solve xy x – 3(0) = 12 2x = 12 x = 6

Replace the x in the equation with zero and solve xy (0) – 3y = 12 -3y = 12 y = -4

Find the x and y intercepts for this equation x + 3y = -6 xy 0 0

Now solve this equation for y and check the intercepts in the calculator x + 3y = -6 xy

Carol is buying T- shirts and caps for her class fundraiser. The caps cost $5 and the T-shirts cost $8. She has $120 to spend. Write an equation for this problem

Let x be the number of caps Let y be the number of T-Shirts 5x + 8y = 120 Find the x and y intercepts

What do these points represent? 5x + 8y = 120 xy

Carol can purchase 24 caps and 0 shirts. She can also purchase 0 caps and 15 shirts xy

Graph this equation What do you notice about this graph? As the number of caps increase, the number of T-shirts decrease. This line has a negative slope

Complete Activity 4c Find x and y intercepts Graph equations using x and y intercepts Check x and y intercepts in calculator Solve problems using x and y intercepts