How to find the roots of this polynomial over $\mathbb{C}$?

Question

Let $s\in\mathbb{Z}$, $i=\sqrt{-1}$ and $a,b\in\mathbb{R}$. Suppose we have the following equation $$\bigg((-1)^{s-1}x^{2s-2}-ibx+a\bigg)\bigg((-1)^{s-1}x^{2s-2}+ibx+a\bigg)=0$$ How would I go about finding its roots (in $\mathbb{C}$)? I think it makes sense to split into the cases where s is even or odd, but im still not sure what to do, the terms with $b$ in them are throwing me off.