Negative to the power of an irrational.

$(-a)^{b}=ae^{ib\pi +2ki\pi}= a\cos(b\pi + 2k\pi)+ai\sin(b\pi + 2k\pi) \qquad k\in \mathbb{Z}$

So $x$ is only real if $\sin(b\pi)=0$ , this only happens for $b\in \mathbb{Z} \implies \sin(b\pi)\neq 0 \implies \boxed{x\,\text{is never real}}$