Calculus 8th Edition

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

Chapter 2 - Derivatives - 2.3 Differentiation Formulas - 2.3 Exercises - Page 142: 74

Answer

$a) P'(2)=\frac{3}{2}$ $b) Q'(7)=\frac{43}{12}$

Work Step by Step

$$P'(x)=F'(x)G(x)+F(x)G'(x)$$ $$P'(2)=F'(2)G(2)+F(2)G'(2)$$ At $x=2$,$F(2)=3$ and the graph of $F$ has a horizontal asymptote so $F'(2)=0$. At $x=2$,$G(2)=2$ the value of $G'(2)$ is the slope of the tangent line to $G$ at $x=2$: $$G'(2)=\frac{2-1}{2-0}=\frac{1}{2}$$ so: $$P'(2)=0\cdot 2+3\times\frac{1}{2}=\frac{3}{2}$$ ---------------------------------------------------------------------- $$Q'(7)=\frac{F'(7)G(7)-F(7)G'(7)}{G^{2}(7)}$$ At $x=7$,$F(7)=5$ and the slope of the tangent line to $F$ at $7$ is: $$F'(7)=\frac{5-4}{7-3}=\frac{1}{4}$$ At $x=7$,$G(7)=1$ and the slope of the tangent line to $G$ at $7$ is: $$G'(7)=\frac{1-3}{7-4}=\frac{-2}{3}$$ so: $$Q'(7)=\frac{\frac{1}{4}\cdot 1-5\cdot (\frac{-2}{3})}{1^{2}}=\frac{43}{12}$$
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