University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 4 - Section 4.1 - Extreme Values of Functions - Exercises - Page 216: 51

Answer

the critical points are: (0,0), (4,-48)

Work Step by Step

Given $y={(x)^2}-32\sqrt{x}$ The critical point occurs where the first derivative is zero: $\frac{dy}{dx}=\frac{d{({(x)^2}-32\sqrt{x})}}{dx}$ ${\frac{dy}{dx}}={{2x}-\frac{32}{2\sqrt{x}}}$ ${\frac{dy}{dx}}=\frac{(4(x^{\frac{3}{2}})-32)}{(2\sqrt{x})}$ so the critical point is ${\frac{dy}{dx}}=0$ $f'(x)=\frac{(4(x^{\frac{3}{2}})-32)}{(2\sqrt{x})}=0$ $x=4$ since denominator is undefined at ${\sqrt{x}}=0$ $x=0,x=4$ the critical value of y can be obtained by putting in the value of x: $y={(x)^2}-32\sqrt{x}=0$ $y={(x)^2}-32\sqrt{x}={(4)^2}-32\sqrt{4}=-48$ thus the critical points are: (0,0), (4,-48)
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