Finite Math and Applied Calculus (6th Edition)

Published by Brooks Cole
ISBN 10: 1133607705
ISBN 13: 978-1-13360-770-0

Chapter 11 - Section 11.3 - The Product and Quotient Rules - Exercises - Page 818: 27

Answer

$\displaystyle \frac{dy}{dx}=\frac{3}{2}\sqrt{x}$

Work Step by Step

$(\sqrt{x}=^{1/2})$ and, for $\sqrt{x}$ to be defined , x can not be negative , so, if needed, $\sqrt{x^{2}}=|x|=x \qquad (*)$ ----------------- $f(x)=x,\ \ \quad g(x)=x^{1/2},\quad y=f(x)\cdot g(x)$ $f^{\prime}(x)=1\displaystyle \qquad g^{\prime}(x)=\frac{1}{2}x^{-1/2}=\frac{1}{2\sqrt{x}}$ $\displaystyle \frac{dy}{dx}=\frac{d}{dx}[f(x)\cdot g(x)]$= ... product rule ... =$f^{\prime}(x)g(x)-f(x)g^{\prime}(x)$ =$ 1\displaystyle \cdot\sqrt{x}+x\cdot\frac{1}{2\sqrt{x}}$ $=\displaystyle \sqrt{x}+\frac{x}{2\sqrt{x}}\cdot\frac{\sqrt{x}}{\sqrt{x}}\quad $...see (*), $\sqrt{x}\sqrt{x}=x$ $=\displaystyle \sqrt{x}+\frac{x\sqrt{x}}{2x}$ $=\displaystyle \sqrt{x}+\frac{\sqrt{x}}{2}$ $=\displaystyle \frac{3}{2}\sqrt{x}$
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