Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 1 - Equations and Inequalities - 1.6 Other Types of Equations and Applications - 1.6 Exercises - Page 148: 89

Answer

$\{\pm\sqrt 3, \pm i\sqrt 5\}$

Work Step by Step

Step 1. Let $u=x^2$, we have $u^2+2u-15=0$ Step 2. Factor and solve: $(u+5)(u-3)=0$ thus $u=-5, 3$ Step 3. For $u=-5$, we have $x^2=-5$ and $x=\pm i\sqrt 5$ Step 4. For $u=3$, we have $x^2=3$ and $x=\pm\sqrt 3$ Step 5. Solution set $\{\pm\sqrt 3, \pm i\sqrt 5\}$
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