## Calculus 10th Edition

$f''(x)=-\dfrac{16}{5x\sqrt[5]{x^4}}.$
$f(x)=20x^{\frac{1}{5}}$ Using the Power Rule: $f'(x)=(\frac{1}{5})(20)(x^{\frac{1}{5}-1})=\dfrac{4}{\sqrt[5]{x^4}}.$ Using the Power Rule: $f''(x)=(-\frac{4}{5})(4)x^{-\frac{4}{5}-1}=-\dfrac{16}{5x\sqrt[5]{x^9}}.$