Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 2 - The Derivative - 2.1 Tangent Lines And Rates Of Change - Exercises Set 2.1 - Page 120: 13

Answer

a) The average rate of change of y=$m_{sec}$=$\frac{-1}{6}$ b) Instantaneous rate of change of y at specific value of $x_{0} $=$m_{tan}$=$-\frac{1}{4}x_{y}$

Work Step by Step

a) find the average rate of change of y w.r.t x over intervals$ x_{0}$ and $ x_{1}$. Given: y=$\frac{1}{x}$ let y=f(x)=$\frac{1}{x}$ since we have $ x_{0}$=2 and $ x_{1}$=3 then we get f($ x_{0}$)=f(2)=$\frac{1}{2}$ and f($ x_{1}$)=f(3)=$\frac{1}{3}$ Now, The average rate of change of y=$m_{sec}$=$\frac{f( x_{1})-f(x_{0})}{x_{1}-x_{0}}$ putting values, The average rate of change of y=$m_{sec}$=$\frac{\frac{1}{2}-\frac{1}{3}}{3-2}$ =$\frac{\frac{-1}{6}}{1}$ The average rate of change of y=$m_{sec}$=$\frac{-1}{6}$ b) As we know that the specific value of $x_{0}$ =1, then $f( x_{1})=\frac{1}{x_{1}}$ and $f(x_{0})=\frac{1}{2}$ Instantaneous rate of change of y at specific value of $x_{0} $=$m_{tan}$ =$\lim\limits_{x_{1} \to 2}$$\frac{f( x_{1})-f(x_{0})}{x_{1}-x_{0}}$ =$\lim\limits_{x_{1} \to 2}$$\frac{( \frac{1}{x_{1}})-\frac{1}{2})}{x_{1}-2}$ =$\lim\limits_{x_{1} \to 2}$$\frac{( \frac{2-x_{1}}{2x_{1}})}{x_{1}-2}$ =$\lim\limits_{x_{1} \to 2}$$-\frac{( \frac{-2+x_{1}}{2x_{1}})}{x_{1}-2}$ =$\lim\limits_{x_{1} \to 2}$$-\frac{( \frac{1}{2x_{1}})}{1}$ =$\lim\limits_{x_{1} \to 2}$$-\frac{1}{2x_{1}}$ Applying limit =$-\frac{1}{2(2)}$ Instantaneous rate of change of y at specific value of $x_{0} $=$m_{tan}$=$-\frac{1}{4}$ c) The arbitrary value of $x_{0}$ =$x_{0}$ then $f( x_{1})=\frac{1}{x_{1}}$ and $f(x_{0})=\frac{1}{{x_{0}}}$ Instantaneous rate of change of y at arbitrary value of $x_{0} $=$m_{tan}$ =$\lim\limits_{x_{1} \to x_{0}}$$\frac{f( x_{1})-f(x_{0})}{x_{1}-x_{0}}$ =$\lim\limits_{x_{1} \to x_{0}}$$\frac{( \frac{1}{x_{1}})-\frac{1}{ x_{0}})}{x_{1}- x_{0}}$ =$\lim\limits_{x_{1} \to x_{0}}$$\frac{( \frac{ x_{0}-x_{1}}{ x_{0}x_{1}})}{x_{1}- x_{0}}$ =$\lim\limits_{x_{1} \to x_{0}}$$-\frac{( \frac{- x_{0}+x_{1}}{ x_{0}x_{1}})}{x_{1}- x_{0}}$ =$\lim\limits_{x_{1} \to x_{0}}$$-\frac{( \frac{1}{ x_{0}x_{1}})}{1}$ =$\lim\limits_{x_{1} \to x_{0}}$$-\frac{1}{ x_{0}x_{1}}$ Applying limit =$-\frac{1}{ x_{0}( x_{0})}$ Instantaneous rate of change of y at specific value of $x_{0} $=$m_{tan}$=$-\frac{1}{x_{0}^{2}}$ take value of ${x_{0}}$ as 1,2,3,4,5,...... d) put value of ${x_{0}}$= 2 and ${x_{1}}$=3 in y=$\frac{1}{x}$ at $x_{0}$=2 f($ x_{0}$)=f(2)=$\frac{1}{2}$ (2, $\frac{1}{2}$ ) f($ x_{1}$)=f(3)=$\frac{1}{3}$ at $ x_{1}$ =3 (3, $\frac{1}{3}$) graph :
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