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: 23

Answer

one-to-one function inverse: $f^{-1}(x)=\sqrt[3]{x+4}$

Work Step by Step

Some of the ordered pairs of the given function, $ f(x)=x^3-4 $, are $ \left\{(-2,-12)(-1,-5),(0,-4),(1,-3),(2,4),...\right\} $. Note that every $y$-coordinate from this function is unique. Hence, the given function is a one-to-one function. To find the inverse, let $y=f(x)$. Then, interchange the $x$ and $y$ variables and solve for $y$. That is, \begin{align*}\require{cancel} y&=x^3-4 \\&\Rightarrow x=y^3-4 &(\text{interchange $x$ and $y$}) \\& x+4=y^3 &(\text{solve for $y$}) \\& \sqrt[3]{x+4}=y \\& y=\sqrt[3]{x+4} .\end{align*} Hence, the inverse is $ f^{-1}(x)=\sqrt[3]{x+4} $.
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