Thomas' Calculus 13th Edition

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

Chapter 4: Applications of Derivatives - Section 4.3 - Monotonic Functions and the First Derivative Test - Exercises 4.3 - Page 203: 51

Answer

$(a)$ Local maximum: $(0,2)$ local minimum: $(2-\sqrt{3},1.866).$ $(b)$ Absolute maximum: none. Absolute minimum: $(2-\sqrt{3},1.866).$ $(c)$ See graph.

Work Step by Step

$g(x)=\displaystyle \frac{x-1}{x^{2}-1},\quad x\in[0,1)$ $g'(x)=\displaystyle \frac{1(x^{2}-1)-(x-2)(2x)}{(x^{2}-1)^{2}}=\frac{-x^{2}+4x-1}{(x-1)^{2}(x+1)^{2}}=-\frac{x^{2}-4x+1}{(x-1)^{2}(x+1)^{2}}$ $g'(x)$ is undefined for $ x=\pm 1$: not critical points (not in the domain). $g'(x)=0$ for $x=\displaystyle \frac{4\pm\sqrt{16-4}}{2}=\frac{4\pm 2\sqrt{3}}{2}=2\pm\sqrt{3}$ In the interval $[0,1)$, x$=2-\sqrt{3}\approx 0.2679$ is the sole critical point. $\left[\begin{array}{llllll} interval & [ & (-2,0) & 2-\sqrt{3} & (0,1) & )\\ t & 0 & 0.1 & 1 & 0.5 & 1\\ f'(t) & & -0.89 & & 1.333 & \\ f(t) & 2 & \searrow & 1.866 & \nearrow & ...\\ & & & & & \end{array}\right]$ $(a)$ Local maximum: $(0,2)$ local minimum: $(2-\sqrt{3},1.866).$ $(b)$ Absolute maximum: none. Absolute minimum: $(2-\sqrt{3},1.866).$ $(c)$ See graph.
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