Calculus 8th Edition

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

Chapter 2 - Derivatives - 2.3 Differentiation Formulas - 2.3 Exercises - Page 141: 61


$$f'(x)=\frac{2x+2x^2}{(1+2x)^2}$$ $$f''(x)=\frac{2}{(1+2x)^3}$$

Work Step by Step

$$f(x)=\frac{x^2}{1+2x}$$ Differentiating with respect to $x$, using quotient's rule, $$f'(x)=\frac{(2x)(1+2x)-x^2(2)}{(1+2x)^2}=\frac{2x+2x^2}{(1+2x)^2}$$ Differentiating again with respect to $x$, using quotient's rule, $$f''(x)=\frac{(2+4x)(1+2x)^2-(2x+2x^2)(2(1+2x)(2))}{(1+2x)^4}$$ $$f''(x)=\frac{2(1+2x)^3-8x(1+x)(1+2x)}{(1+2x)^4}=\frac{2(1+2x)^2-8x(1+x)}{(1+2x)^3}$$ $$f''(x)=\frac{2(1+4x^2+4x)-8x-8x^2}{(1+2x)^3}\implies f''(x)=\frac{2}{(1+2x)^3}.$$
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