Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 2 - Differentiation - 2.5 Exercises - Page 145: 18

Answer

a. equation: $y=±\sqrt{\frac{25}{3}-\frac{25}{36}x^2}$ b. derivatives: $y'=-\frac{25x}{36y}$

Work Step by Step

1. Rewrite the equation in terms of x: $36y^2=300-25x^2$ $y^2=\frac{300}{36}-\frac{25}{36}x^2$ = $y^2= \frac{25}{3}-\frac{25}{36}x^2$ $\sqrt {y^2}= \sqrt {\frac{25}{3}-\frac{25}{36}x^2}$ a. $y= ± \sqrt{\frac{25}{3}-\frac{26}{36}x^2}$ 2. Find the derivative of $y= ± \sqrt{\frac{25}{3}-\frac{26}{36}x^2}$ $y'= \frac {d}{dx} (- \sqrt{\frac{25}{3}-\frac{26}{36}x^2})$ $y'= \frac {d}{dx} (-\sqrt {\frac{300-25x^2}{36}})$ $y'=\frac{d}{dx}(-\frac{\sqrt{300-25x^2}}{6})$ $y'= -\frac{1}{6}\times\frac{d}{dx}(\sqrt{300-25x^2})$ $y' = -\frac{1}{6}\times(\frac{1}{2\sqrt{300-25x^2}})(-25)(2x) $ $y'= \frac{5x}{6\sqrt{12-x^2}}$ $y'= \frac {d}{dx} ( \sqrt{\frac{25}{3}-\frac{26}{36}x^2})$ $y'= \frac {d}{dx} (\sqrt {\frac{300-25x^2}{36}})$ $y'=\frac{d}{dx}(\frac{\sqrt{300-25x^2}}{6})$ $y'= \frac{1}{6}\times\frac{d}{dx}(\sqrt{300-25x^2})$ $y' = \frac{1}{6}\times(\frac{1}{2\sqrt{300-25x^2}})(-25)(2x) $ $y'= -\frac{5x}{6\sqrt{12-x^2}}$ 3. Find the derivative of: $25x^2+36y^2=300$ $\frac{d}{dx} (25x^2) + \frac{d}{dx}(36y^2)= \frac{d}{dx}(300)$ $50x +72y (\frac{dy}{dx}) = 0$ b. $\frac{dy}{dx}= \frac{-50x}{72y} = -\frac{25x}{36y}$ 4. Graph:
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