Calculus with Applications (10th Edition)

Published by Pearson
ISBN 10: 0321749006
ISBN 13: 978-0-32174-900-0

Chapter 4 - Calculating the Derivative - Chapter Review - Review Exercises - Page 245: 52

Answer

${\bf{a}}. - \frac{{36}}{{13}};$ ${\bf{b}}. - \frac{{21}}{{10}}$

Work Step by Step

$$\eqalign{ & {\bf{a}}.{\text{ }}{D_x}\left( {g\left[ {f\left( x \right)} \right]} \right){\text{ }} \cr & {\text{By using the chain rule}} \cr & {D_x}\left( {g\left[ {f\left( x \right)} \right]} \right) = g'\left[ {f\left( x \right)} \right]f'\left( x \right) \cr & {\text{At }}x = 2 \cr & = g'\left[ {f\left( 2 \right)} \right]f'\left( 2 \right) \cr & {\text{From the table }}f\left( 2 \right) = 4{\text{ and }}f'\left( 2 \right) = - 6 \cr & g'\left[ {f\left( 2 \right)} \right]f'\left( 2 \right) = g'\left( 4 \right)\left( { - 6} \right) \cr & {\text{From the table }}g'\left( 4 \right) = \frac{6}{{13}},{\text{ then}} \cr & g'\left[ {f\left( 2 \right)} \right]f'\left( 2 \right) = \left( {\frac{6}{{13}}} \right)\left( { - 6} \right) \cr & g'\left[ {f\left( 2 \right)} \right]f'\left( 2 \right) = - \frac{{36}}{{13}} \cr & \cr & {\bf{b}}.{\text{ }}{D_x}\left( {g\left[ {f\left( x \right)} \right]} \right){\text{ }} \cr & {\text{By using the chain rule}} \cr & {D_x}\left( {g\left[ {f\left( x \right)} \right]} \right) = g'\left[ {f\left( x \right)} \right]f'\left( x \right) \cr & {\text{At }}x = 3 \cr & = g'\left[ {f\left( 3 \right)} \right]f'\left( 3 \right) \cr & {\text{From the table }}f\left( 3 \right) = 2{\text{ and }}f'\left( 3 \right) = - 7 \cr & g'\left[ {f\left( 3 \right)} \right]f'\left( 3 \right) = g'\left( 2 \right)\left( { - 7} \right) \cr & {\text{From the table }}g'\left( 2 \right) = \frac{3}{{10}},{\text{ then}} \cr & g'\left[ {f\left( 3 \right)} \right]f'\left( 3 \right) = \left( {\frac{3}{{10}}} \right)\left( { - 7} \right) \cr & g'\left[ {f\left( 3 \right)} \right]f'\left( 3 \right) = - \frac{{21}}{{10}} \cr} $$
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