Answer
$x=\pm4i$ or $x=\pm1$
Work Step by Step
$x^4+15x^2-16=(x^2+16)(x^2-1)$
Thus $x^2-1=0\\x^2=1\\x=\pm1$ or $x^2+16=0\\x^2=-16\\x=\pm4i$
Algebra 2 (1st Edition)
by Larson, Ron; Boswell, Laurie; Kanold, Timothy D.; Stiff, Lee
Published by
McDougal Littell
ISBN 10:
0618595414
ISBN 13:
978-0-61859-541-9
Chapter 5 Polynomials and Polynomial Functions - 5.7 Apply the Fundamental Theorem of Algebra - 5.7 Exercises - Skill Practice - Page 384: 14
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