Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 3 - Section 3.4 - The Chain Rule - 3.4 Exercises - Page 205: 60

Answer

The point is $(4,3)$.

Work Step by Step

Let's first look at the line $6x+2y=1$ and rearrange it so that it's in the form $y=mx+b$. $6x+2y=1$ $2y=1-6x$ $y=\frac{1}{2}-3x$ $y=-3x+\frac{1}{2}$ We see that the slope of this line is $-3$. We now need to find the slope of a line that would be perpendicular to this line by finding the opposite reciprocal of $-3$, which is $\frac{1}{3}$. This means that we want to find the $x$ value that gives us $y'(x)=\frac{1}{3}$. $y=\sqrt {1+2x}=(1+2x)^{\frac{1}{2}}$ We'll be using the power rule. To refresh your memory: $y=u^n$ $y'=n'u^{n-1}$ So $y'=\frac{1}{2}(1+2x)^{-\frac{1}{2}}*2$ $y'=\frac{1}{\sqrt{1+2x}}=\frac{1}{3}$ $\sqrt{1+2x}=3$ $1+2x=9$ $2x=8$ $x=4$ And the point is $(4,3)$.
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