Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 3: Derivatives - Practice Exercises - Page 179: 86

Answer

tangent $y=-\frac{1}{4}x+\frac{17}{4}$ normal $y=4x$

Work Step by Step

Step 1. Given $x^{3/2}+2y^{3/2}=17$, we have $\frac{3}{2}x^{1/2}+3y^{1/2}y'=0$ or $y'=-\frac{\sqrt x}{2\sqrt y}$ which gives the slope of tangent lines to the curve. Step 2. At point $(1,4)$, the slope of the tangent line is $m=-\frac{\sqrt 1}{2\sqrt 4}=-\frac{1}{4}$ and the equation is $y-4=-\frac{1}{4}(x-1)$ or $y=-\frac{1}{4}x+\frac{17}{4}$ Step 3. The slope of the normal line is $n=-1/m=4$ and the equation is $y-4=4(x-1)$ or $y=4x$
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