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: 70

Answer

$\left\{\dfrac{2}{3},2\right\}$

Work Step by Step

Let $z= (x-1)^{-1} $. Then the given equation, $ 3-2(x-1)^{-1}=(x-1)^{-2} ,$ is equivalent to \begin{align*}\require{cancel} 3-2z&=z^2 \\ 0&=z^2+2z-3 \\ z^2+2z-3&=0 .\end{align*} Using factoring of trinomials, the equation above is equivalent to \begin{align*} (z+3)(z-1)&=0 .\end{align*} Equating each factor to zero (Zero Product Property) and solving for the variable, then \begin{array}{l|r} z+3=0 & z-1=0 \\ z=-3 & z=1 .\end{array} Since $z= (x-1)^{-1}=\dfrac{1}{x-1} ,$ by back substitution, then \begin{array}{l|r} \dfrac{1}{x-1}=-3 & \dfrac{1}{x-1}=1 .\end{array} By cross-multiplication and the properties of equality, the equations above are equivalent to \begin{array}{l|r} 1(1)=-3(x-1) & 1(1)=1(x-1) \\ 1=-3x+3 & 1=x-1 \\ 3x=3-1 & 1+1=x \\ 3x=2 & 2=x \\\\ x=\dfrac{2}{3} & x=2 .\end{array} Checking the solutions by substitution in the given equation results to \begin{array}{l|r} \text{If }x=\dfrac{2}{3}: & \text{If }x=2 \\\\ 3-2\left(\dfrac{2}{3}-1\right)^{-1}\overset{?}=\left(\dfrac{2}{3}-1\right)^{-2} & 3-2(2-1)^{-1}\overset{?}=(2-1)^{-2} \\\\ 3-2\left(-\dfrac{1}{3}\right)^{-1}\overset{?}=\left(-\dfrac{1}{3}\right)^{-2} & 3-2(1)^{-1}\overset{?}=(1)^{-2} \\\\ 3-2\left(-\dfrac{3}{1}\right)^{1}\overset{?}=\left(-\dfrac{3}{1}\right)^{2} & 3-2(1)\overset{?}=1 \\\\ 3+6\overset{?}=9 & 3-2\overset{?}=1 \\ 9\overset{\checkmark}=9 & 1\overset{\checkmark}=1 .\end{array} Since all solutions satisfy the original equation, then the solution set of the equation $ 3-2(x-1)^{-1}=(x-1)^{-2} $ is $\left\{\dfrac{2}{3},2\right\}$.
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