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 732: 38

Answer

$m=81$ or $m=16$

Work Step by Step

$ m^{\frac{1}{2}}+6=5m^{\frac{1}{4}}\qquad$... add $-5m^{\frac{1}{4}}$ to both sides. $ m^{\frac{1}{2}}-5m^{\frac{1}{4}}+6=0\qquad$...substitute $m^{\frac{1}{4}}$ for $u$ so that $u^{2}=m^{\frac{1}{2}}$ Note that $m^{\frac{1}{4}}$ is the fourth root of $t$, a positive number. $ u^{2}-5u+6=0\qquad$... solve with the Quadratic formula. $u=\displaystyle \frac{-b\pm\sqrt{b^{2}-4ac}}{2a}$ $u=\displaystyle \frac{5\pm\sqrt{25-24}}{2}$ $u=\displaystyle \frac{5\pm\sqrt{1}}{2}$ $u=\displaystyle \frac{5\pm 1}{2}$ $u=\displaystyle \frac{5+1}{2}=\frac{6}{2}=3$ or $u=\displaystyle \frac{5-1}{2}=\frac{4}{2}=2$ Bring back $m^{\frac{1}{4}}=u$. $m^{\frac{1}{4}}=3$ or $ m^{\frac{1}{4}}=2\qquad$...raise both sides of both expressions to the fourth power. $(m^{\frac{1}{4}})^{4}=3^{4}$ or $(m^{\frac{1}{4}})^{4}=2^{4} $ $m=81$ or $m=16$
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