Intermediate Algebra (12th Edition)

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

Chapter 9 - Section 9.1 - Inverse Functions - 9.1 Exercises - Page 589: 30

Answer

$f(^{-1}(x)=\dfrac{4x+2}{3(x+1)},\text{ }x\ne-1$

Work Step by Step

Let $y=f(x)$. Then the given one-to-one function, $ f(x)=\dfrac{-3x+2}{3x-4},\text{ }x\ne\dfrac{4}{3} ,$ becomes \begin{align*}\require{cancel} y&=\dfrac{-3x+2}{3x-4},\text{ }x\ne\dfrac{4}{3} .\end{align*} To find the inverse, interchange the $x$ and $y$ variables and then solve for $y$. That is, \begin{align*} x&=\dfrac{-3y+2}{3y-4} &(\text{interchange $x$ and $y$}) \\\\ (3y-4)(x)&=\left(\dfrac{-3y+2}{\cancel{3y-4}}\right)(\cancel{3y-4}) &(\text{solve for $y$}) \\\\ 3xy-4x&=-3y+2 \\ 3xy+3y&=4x+2 \\ 3y(x+1)&=4x+2 \\\\ \dfrac{\cancel3y(\cancel{x+1})}{\cancel3(\cancel{x+1})}&=\dfrac{4x+2}{3(x+1)} \\\\ y&=\dfrac{4x+2}{3(x+1)},\text{ }x\ne-1 .\end{align*} Hence, the inverse of $ f(x)=\dfrac{-3x+2}{3x-4},\text{ }x\ne\dfrac{4}{3} $ is $ f(^{-1}(x)=\dfrac{4x+2}{3(x+1)},\text{ }x\ne-1 $.
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