Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 7: Transcendental Functions - Section 7.1 - Inverse Functions and Their Derivatives - Exercises 7.1 - Page 373: 27

Answer

$$ f^{-1}(x) =\sqrt[3 ]{x-1}$$ Domain of $ f^{-1}$ is $(-\infty,\infty)$ Range of $ f^{-1}$ is $(-\infty,\infty)$

Work Step by Step

Given $$ f(x) =x^{3}+1$$ Find the inverse: \begin{aligned} y &=x^{3}+1 \\ x^3 &=y-1 \\ x&=\sqrt[3]{y-1} \\ \text {Switch }& x \ and\ y: \text{}\\ y=&\sqrt[3]{x-1} =f^{-1}(x) \end{aligned} We see that: Domain of $ f^{-1}$ is $(-\infty,\infty)$ and Range of $ f^{-1}$ is $(-\infty,\infty)$ Confirm the inverse: \begin{aligned} f\left(f^{-1}(x)\right) &=f(\sqrt[3]{x-1}) \\ &=(\sqrt[3]{x-1})^{3}+1 \\ &=x +1-1 \\&=x \\ f^{-1}(f(x)) &=f^{-1}\left(x^{3}+1\right) \\ &=\sqrt[3]{x^{3}+1-1} \\ &=\sqrt[3]{x^{3} } \\ &=x \end{aligned}
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