Calculus, 10th Edition (Anton)

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

Chapter 2 - The Derivative - 2.7 Implicit Differentiation - Exercises Set 2.7 - Page 166: 20

Answer

At $(10,3), \frac{dy}{dx} = \frac{1}{6}$ At $(10,-3), \frac{dy}{dx} = -\frac{1}{6}$

Work Step by Step

First method: We solve for y and then take the derivative: $y^2-x+1 = 0$ $y = \pm \sqrt{x-1}$ $\frac{dy}{dx} = \pm \frac{1}{2} (x-1)^{-\frac{1}{2}}$ Using this formula, we get: At $(10,3), \frac{dy}{dx} = \frac{1}{6}$ (because the slope is upward in the first quadrant, we take the positive $\frac{dy}{dx}$ value). At $(10,-3), \frac{dy}{dx} = -\frac{1}{6}$ (because the slope is downward in the fourth quadrant, we take the negative $\frac{dy}{dx}$ value). Second Method: We use implicit differentiation. $y^2 -x+1= 0$ $2y\frac{dy}{dx}-1 = 0$ $\frac{dy}{dx} = \frac{1}{2y}$ Using this formula, we get: At $(10,3), \frac{dy}{dx} = \frac{1}{6}$ At $(10,-3), \frac{dy}{dx} = -\frac{1}{6}$
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