University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 4 - Section 4.2 - The Mean Value Theorem - Exercises - Page 223: 14

Answer

$f(x)$ satisfies the hypotheses because $f(x)$ is continuous on $[0,3]$ $f'(x)$ is defined on $(0,3)$

Work Step by Step

The Mean Value Theorem requires - that $f(x)$ is continuous on $[a,b]$ - that $f'(x)$ is defined on $(a,b)$ Here, $[a,b]=[0,3]$ Polynomials are continuous functions. The only problem might arise at $x=2.$ $\displaystyle \lim_{x\rightarrow 2^{-}}f(x)=2(2)-3=1$ $\displaystyle \lim_{x\rightarrow 2^{+}}f(x)=6(2)-(2)^{2}-7=1$ and, $f(2)=1$, so f is continuous on $[0,3]$. $f'(x)=\left\{\begin{array}{ll} 2, & 0\leq x\leq 2\\ 6-2x & 2\lt x\leq 3 \end{array}\right.$ $\displaystyle \lim_{x\rightarrow 2^{-}}f'(x)=2$ $\displaystyle \lim_{x\rightarrow 2^{+}}f'(x)=6-2(2)=2$ so $f'(x)$ is differentiable on $(0,3)$ Both conditions are satisfied.
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