Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 2 - Derivatives - 2.5 The Chain Rule - 2.5 Exercises - Page 159: 65

Answer

(a) $u'(1)$ = $\frac{3}{4}$ (b) $v'(x)$ does not exist (c) $w'(1)$ = $-2$

Work Step by Step

(a) $u(x)$ = $f(g(x))$ $u'(x)$ = $f'(g(x))g'(x)$ so $u'(1)$ = $f'(g(1))g'(1)$ $u'(1)$ = $f'(3)g'(1)$ find $f'(3)$ from (2,4) to (6,3) $m$ = $\frac{3-4}{6-2}$ = $-\frac{1}{4}$ so $f'(3)$ = $-\frac{1}{4}$ find $g'(1)$ from (0,6) to (2,0) $m$ = $\frac{0-6}{2-2}$ = $-3$ so $g'(1)$ = $-3$ Thus $u'(1)$ = $f'(3)g'(1)$ $u'(1)$ = $-\frac{1}{4}(-3)$ $u'(1)$ = $\frac{3}{4}$ (b) $v(x)$ = $g(f(x))$ $v'(x)$ = $g'(f(x))f'(x)$ $v'(1)$ = $g'(f(1))f'(1)$ $v'(1)$ = $g'(2)f'(1)$ which does not exist since $g'(2)$ does not exist (c) $w(x)$ = $g(g(x))$ $w'(x)$ = $g'(g(x))g'(x)$ $w'(1)$ = $g'(g(1))g'(1)$ $w'(1)$ = $g'(3)g'(1)$ find $g'(3)$ from (2,0) to (5,2) $m$ = $\frac{2-0}{5-2}$ = $\frac{2}{3}$ so $g'(1)$ = $\frac{2}{3}$ Thus $w'(1)$ = $\frac{2}{3}(-3)$ = $-2$
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