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Intercepts Help

By — McGraw-Hill Professional
Updated on Sep 26, 2011

Intercepts

y-Intercepts

The point on the graph where a line crosses the y axis is called the y intercept (see Fig. 11-21 ).

Intercepts

Fig. 11-21.

To find the y intercept, let x = 0 and substitute in the equation, and then solve for y .

Example 1

Find the y intercept of 2x + 3y = 9.

Solution 1

Substitute 0 for x and solve for y:

Intercepts

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

x-Intercepts

The point on the graph where a line crosses the x axis is called the x intercept (see Fig. 11-22).

Intercepts

Fig. 11-22.

To find the x intercept, let y = 0 and substitute in the equation, and then solve for x .

Example 2

Find the x intercept for 5x + 2y = 30.

Solution 2

Substitute 0 for y and solve for x:

Intercepts

Hence, the x intercept is (6, 0).

Math Note: It is easy to draw lines on a graph using the intercepts for the two points.

Intercepts Practice Problems

Practice

1. Find the x intercept of 5x + 4y = 30

2. Find the y intercept of x - 7y = 14

3. Find the y intercept of 2x + 8y = 24

4. Find the x intercept of 3x - 17y = 21

5. Find the y intercept of x + 5y = -20

Answers

1. (6, 0)

2. (0, -2)

3. (0, 3)

4. (7, 0)

5. (0, -4)

Practice problems for these concepts can be found at: Graphing Practice Test.

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