Calculus 8th Edition

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

Chapter 2 - Derivatives - 2.5 The Chain Rule - 2.5 Exercises - Page 160: 84

Answer

\[\left(\frac{f(x)}{g(x)}\right)'=\frac{f'(x)g(x)-f(x)g'(x)}{[g(x)]^2}\]

Work Step by Step

We can rewrite \[\frac{f(x)}{g(x)}=f(x)\cdot [g(x)]^{-1}\] Differentiate with respect to $x$ using chain rule \[\left(\frac{f(x)}{g(x)}\right)'=f(x)\cdot \{[g(x)]^{-1}\}'+\{f(x)\}'[g(x)]^{-1}\] \[\left(\frac{f(x)}{g(x)}\right)'=(-1)f(x)\cdot [g(x)]^{-2}+f'(x)[g(x)]^{-1}\] \[\left(\frac{f(x)}{g(x)}\right)'=-\frac{f(x)}{[g(x)]^2}+\frac{f'(x)}{[g(x)]}\] \[\left(\frac{f(x)}{g(x)}\right)'=\frac{f'(x)g(x)-f(x)g'(x)}{[g(x)]^2}\] Hence \[\left(\frac{f(x)}{g(x)}\right)'=\frac{f'(x)g(x)-f(x)g'(x)}{[g(x)]^2}\]
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