Intermediate Algebra (12th Edition)

Published by Pearson
ISBN 10: 0321969359
ISBN 13: 978-0-32196-935-4

Chapter 8 - Section 8.3 - Equations Quadratic in Form - 8.3 Exercises - Page 530: 79

Answer

$\left\{\dfrac{4}{3},\dfrac{9}{4}\right\}$

Work Step by Step

Let $z= (2w-3)^{-1} $. Then the given equation, $ 6=7(2w-3)^{-1}+3(2w-3)^{-2} ,$ is equivalent to \begin{align*} 6&=7z+3z^2 \\ 0&=7z+3z^2-6 \\ 3z^2+7z-6&=0 .\end{align*} Using factoring of trinomials, the equation above is equivalent to \begin{align*} (z+3)(3z-2)&=0 .\end{align*} Equating each factor to zero (Zero Product Property) and solving for the variable, then \begin{array}{l|r} z+3=0 & 3z-2=0 \\ z=-3 & 3z=2 \\\\ & z=\dfrac{2}{3} .\end{array} Since $z= (2w-3)^{-1}=\dfrac{1}{2w-3} $, by back-substitution, \begin{array}{l|r} \dfrac{1}{2w-3}=-3 & \dfrac{1}{2w-3}=\dfrac{2}{3} .\end{array} By cross-multiplication, the equations above are equivalent to \begin{array}{l|r} -3(2w-3)=1(1) & 1(3)=2(2w-3) \\ -6w+9=1 & 3=4w-6 \\ -6w=1-9 & 3+6=4w \\ w=\dfrac{-8}{-6} & 9=4w \\ w=\dfrac{4}{3} & \dfrac{9}{4}=w \\ & w=\dfrac{9}{4} .\end{array} Hence, the solution set of the equation $ 6=7(2w-3)^{-1}+3(2w-3)^{-2} $ is $\left\{\dfrac{4}{3},\dfrac{9}{4}\right\}$.
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