Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 3 - The Derivative In Graphing And Applications - 3.1 Analysis Of Functions I: Increase, Decrease, and Concavity - Exercises Set 3.1 - Page 195: 25

Answer

See explanation.

Work Step by Step

\[ \left(-1+x^{2 / 3}\right)^{2}=f(x) \] Differentiate \[ f^{\prime}(x)=2\left(-1+x^{2 / 3} \right) \cdot \frac{2}{3} x^{-1 / 3}=\frac{4}{3}\left(x^{1 / 3}-x^{-1 / 3}\right) \] Differentiate \[ f^{\prime \prime}(x)=\frac{4}{3}\left(\frac{1}{3} x^{-4 / 3}+\frac{1}{3} x^{-2 / 3}\right)=\frac{4 x^{-4 / 3}}{9}\left(1+x^{2 / 3}\right) \] (a) $f(x)$ is increasing on (-1,0)$\cup(1, \infty)$ When $f^{\prime}$ is positive, $f$ is increasing $(\mathbf{b})$ $f(x)$ is decreasing on $(-\infty,-1) \cup(0,1)$ When $f^{\prime}$ is negative, $f$ is decreasing $(c)$ $f(x)$ is concave up on $(-\infty, \infty)$ When $f^{\prime \prime}$ is positive, $f$ is concave up (d) $f(x)$ is never concave down When $f^{\prime \prime}$ is negative, $f$ is concave down $(\mathbf{e})$ When concavity changes and $f$ is continuous, inflection occurs There are no inflection points
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