Answer
not a real number
Work Step by Step
$(-25)^{\frac{5}{2}}=\sqrt (-25)^{5}=\sqrt (-25\times-25\times-25\times-25\times-25)=\sqrt (-25)\times\sqrt (-25)\times\sqrt(-25)\times\sqrt(-25)\times\sqrt(-25)$
We cannot not simplify this any further, as $\sqrt (-25)$ is not a real number. We cannot find a number $a$ such that $a^{2}=-25$.