Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Published by Pearson
ISBN 10: 0-32184-874-8
ISBN 13: 978-0-32184-874-1

Chapter 11 - Quadratic Functions and Equations - 11.5 Equations Reducible to Quadratic - 11.5 Exercise Set - Page 731: 22


$x=\pm i$ or $x=\pm 2i$

Work Step by Step

$ x^{4}+5x^{2}+4=0\qquad$...substitute $x^{2}$ for $u$ $ u^{2}+5u+4=0\qquad$... solve with the Quadractic formula. $u=\displaystyle \frac{-b\pm\sqrt{b^{2}-4ac}}{2a}$ $u=\displaystyle \frac{-5\pm\sqrt{25-16}}{2}$ $u=\displaystyle \frac{-5\pm\sqrt{9}}{2}$ $u=\displaystyle \frac{-5\pm 3}{2}$ $u=\displaystyle \frac{-5+3}{2}=\frac{-2}{2}=-1$ or $u=\displaystyle \frac{-5-3}{2}=\frac{-8}{2}=-4$ Bring back $x^{2}=u$. $x^{2}=-1$ or $x^{2}=-4$ $x=\pm i$ or $x=\pm 2i$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.