Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 2 - Section 2.8 - One-to-One Functions and Their Inverses - 2.8 Exercises - Page 227: 59

Answer

$f^{-1}(x)=\dfrac{x-3}{5x+2}$

Work Step by Step

$f(x)=\dfrac{2x+3}{1-5x}$ Rewrite this expression as $y=\dfrac{2x+3}{1-5x}$ and solve for $x$: $y=\dfrac{2x+3}{1-5x}$ Take $1-5x$ to multiply the left side: $y(1-5x)=2x+3$ $y-5xy=2x+3$ Take $2x$ to the left side and $y$ to the right side: $-5xy-2x=3-y$ Take out common factor $x$ from the left side: $x(-5y-2)=3-y$ Take $-5y-2$ to divide the right side: $x=\dfrac{3-y}{-5y-2}$ $x=\dfrac{y-3}{5y+2}$ Interchange $x$ and $y$: $y=\dfrac{x-3}{5x+2}$ The inverse of the original function is $f^{-1}(x)=\dfrac{x-3}{5x+2}$
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