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: 10

Answer

$\left\{ \dfrac{9-\sqrt{105}}{2},\dfrac{9+\sqrt{105}}{2} \right\}$

Work Step by Step

Multiplying both sides of the given equation, $ \dfrac{5}{x-2}+\dfrac{4}{x+2}=1 ,$ by the $LCD= (x-2)(x+2) $, then, \begin{array}{l}\require{cancel} (x-2)(x+2)\left( \dfrac{5}{x-2}+\dfrac{4}{x+2} \right)=\left( 1 \right)(x-2)(x+2) \\\\ (x+2)(5)+(x-2)(4)=x^2-4 \\\\ 5x+10+4x-8=x^2-4 \\\\ -x^2+(5x+4x)+(10-8+4)=0 \\\\ -x^2+9x+6=0 .\end{array} Using $\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$ (or the Quadratic Formula), the solutions of the quadratic equation, $ -x^2+9x+6=0 ,$ are \begin{array}{l}\require{cancel} \dfrac{-(9)\pm\sqrt{(9)^2-4(-1)(6)}}{2(-1)} \\\\= \dfrac{-9\pm\sqrt{81+24}}{-2} \\\\= \dfrac{-9\pm\sqrt{105}}{-2} \\\\= \dfrac{9\pm\sqrt{105}}{2} .\end{array} Upon checking, both solutions satisfy the original equation. Hence, the solutions are $ \left\{ \dfrac{9-\sqrt{105}}{2},\dfrac{9+\sqrt{105}}{2} \right\} .$
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