Pre-Algebra Demystified

EXAMPLE

Find the y intercept of 2xþ3y¼9.

SOLUTION

Substitute 0 for x and solve for y:

2xþ3y¼ 9

2 ð 0 Þþ3y¼ 9

0 þ3y¼ 9

3y¼ 9

3y

3

¼

9

3

y¼ 3

Hence, the y intercept is (0, 3).

The point on the graph where a line crosses the x axis is called the

x intercept(see Fig. 11-22).

To find the x intercept, let y¼0 and substitute in the equation, and then solve

for x.

EXAMPLE

Find the x intercept for 5xþ2y¼30.

SOLUTION

Substitute 0 for y and solve for x:

220 CHAPTER 11 Graphing

Fig. 11-22.