Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 14 - A Preview of Calculus: The Limit, Derivative, and Integral of a Function - 14.4 The Tangent Problem; The Derivative - 14.4 Assess Your Understanding - Page 898: 24



Work Step by Step

Factor each polynomial: $$f'(-1)\\=\lim_{x\to -1}\frac{f(x)-f(-1)}{x-(-1)}\\=\lim_{x\to -1}\frac{2x^2+1-(2(-1)^2+1))}{x+1}\\=\lim_{x\to -1}\frac{2x^2-2}{x+1}\\=\lim_{x\to -1}\frac{2(x+1)(x-1)}{(x+1)}.$$ Cancel the common factors: $$\lim_{x\to -1}2(x-1)\\=2(-1-1)=-4$$
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