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Your Notes<br />

Example 2 Write an equation of a hyperbola<br />

Write an equation of the<br />

y<br />

hyperbola with foci at<br />

(25, 0) and (5, 0) and<br />

(−4, 0) (4, 0)<br />

vertices at (24, 0) and<br />

(−5, 0)<br />

2<br />

(5, 0)<br />

(4, 0).<br />

The foci and vertices lie on the<br />

-axis equidistant from the<br />

origin, so the transverse axis is<br />

6 x<br />

and the center is the origin. The foci are<br />

each units from the center, so c 5 . The vertices<br />

are each units from the center, so a 5 .<br />

Because c2 5 a2 1 b2 , you have b2 5 c2 2 a2 . Find b2 .<br />

b2 5 c2 2 a2 5 5<br />

Because the transverse axis is horizontal, the standard<br />

form of the equation is as follows:<br />

5 1 Substitute 4 for a and 9 for b 2 .<br />

5 1 Simplify.<br />

Checkpoint Write an equation of the hyperbola with<br />

the given foci and vertices.<br />

2. Foci: (0, 28), (0, 8)<br />

Vertices: (0, 25), (0, 5)<br />

246 Lesson 9.5 Algebra 2 Notetaking Guide Copyright © Holt McDougal. All rights reserved.

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