Calculus 8th Edition

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

Chapter 6 - Inverse Functions - 6.4 Derivatives of Logarithmic Functions - 6.4 Exercises - Page 437: 38

Answer

$y=x-1$

Work Step by Step

Let $f(x)=x^{2}\ln(x)$ The equation of the tangent line to the graph of $f$ at the point $(a,f(a))$ is given by: $y=f(a)+f'(a)(x-a)$ Since the given point is $(1,0)$ it follows that $a=1$ and $f(1)=0$. So the equation of the tangent line to the graph of the given function at $(1,0)$ is: $y=0+f'(1)(x-1)$ Using the product rules for derivatives, the first derivative of $f(x)=x^{2}\ln(x)$ is: $f'(x)=(x^{2})'\ln{(x)}+x^{2}(\ln{(x)})'$ Using the power rules for derivatives, the first derivative of $x^{2}$is $2x$ so: $f'(x)=2x\ln{(x)}+x^{2}(\ln{(x)})'$ The first derivative of the natural logarithm is $\frac{1}{x}$ so: $f'(x)=2x\ln{(x)}+x^{2}\cdot \frac{1}{x}$ Substitute $x=1$ into the equation: $f'(1)=2\cdot 1\cdot \ln{(1)}+1^{2}\cdot \frac{1}{1}$ Simplify the right side it follows: $f'(1)=1$ Substitute $f'(1)=1$ into the equation $y=0+f'(1)(x-1)$ it follows: $y=0+1(x-1)$ Simplify the right side of the equation: $y=x-1$ Therefore, the equation of the tangent line is: $y=x-1$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.