Answer
$\displaystyle \frac{(-3x^{2}+5)\cdot|-x^{3}+5x|}{-x^{3}+5x}$
Work Step by Step
With $u(x)=-x^{3}+5x$,
$\displaystyle \frac{du}{dx}=-3x^{2}+5,$
apply the Generalized Power Rule (see table on p.823)
$\displaystyle \frac{d}{dx}|u|=\frac{|u|}{u}\frac{du}{dx}$
$\displaystyle \frac{d}{dx}|-x^{3}+5x|=\frac{|-x^{3}+5x|}{-x^{3}+5x}\cdot(-3x^{2}+5)$
$=\displaystyle \frac{(-3x^{2}+5)|-x^{3}+5x|}{-x^{3}+5x}$
