Algebra: A Combined Approach (4th Edition)

Published by Pearson
ISBN 10: 0321726391
ISBN 13: 978-0-32172-639-1

Chapter 11 - Section 11.3 - Solving Equations by Using Quadratic Methods - Exercise Set - Page 788: 42

Answer

$x=\frac{-125}{216}, 125$

Work Step by Step

$6x^{2/3}-25x^{1/3}-25=0$ $6(x^{1/3})^2-25x^{1/3}-25=0$ $x^{1/3}=y$ $6(x^{1/3})^2-25x^{1/3}-25=0$ $6y^2-25y-25=0$ $y=(-b±\sqrt{b^2-4ac})/2a$ $y=(-(-25)±\sqrt{(-25)^2-4*6*-25})/2*6$ $y=(25±\sqrt{625+600})/12$ $y=(25±\sqrt{1225})/12$ $y=(25±35)/12$ $y=(25±35)/12$ $y=(25+35)/12$ $y=60/12$ $y=5$ $y=(25-35)/12$ $y=-10/12$ $y=-5/6$ $x^{1/3}=y$ $x^{1/3}=5$ $(x^{1/3})^3=5^3$ $x=125$ $x^{1/3}=y$ $x^{1/3}=-5/6$ $(x^{1/3})^3=(-5/6)^3$ $x=-125/216$
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