## Calculus 8th Edition

{ x | x $\lt$ 0 or x $\gt$ 5 }
Since $\frac{1}{\sqrt[4] x}$ is valid only if x $\gt$ 0, we must have: x² - 5x = x (x - 5) $\gt$ 0, which is valid if: - x and (x - 5) are both positive → x $\gt$ 5; or - x and (x - 5) are both negative → x $\lt$ 0 { x | x $\lt$ 0 or x $\gt$ 5 }