Intermediate Algebra (6th Edition)

Published by Pearson
ISBN 10: 0321785045
ISBN 13: 978-0-32178-504-6

Chapter 8 - Section 8.3 - Solving Equations by Using Quadratic Methods - Exercise Set - Page 501: 19

Answer

The solutions are $x=125$ and $x=-8$

Work Step by Step

$x^{2/3}-3x^{1/3}-10=0$ Let $u$ be equal to $x^{1/3}$ If $u=x^{1/3}$, then $u^{2}=x^{2/3}$ Rewrite the original equation using the new variable $u$: $u^{2}-3u-10=0$ Solve by factoring: $(u+2)(u-5)=0$ Set both factors equal to $0$ and solve each individual equation for $u$: $u+2=0$ $u=-2$ $u-5=0$ $u=5$ Substitute $u$ back to $x^{1/3}$ and solve for $x$: $x^{1/3}=-2$ $x=(-2)^{3}$ $x=-8$ $x^{1/3}=5$ $x=5^{3}$ $x=125$ The solutions are $x=125$ and $x=-8$
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