$8.9 \quad \frac{x^{4}-2 x^{2}-8}{x^{2}+2 x+1}<0$.

$8.9 \quad \frac{x^{4}-2 x^{2}-8}{x^{2}+2 x+1}<0$.
8.9 Factoring the numerator and denominator, we get $\frac{\left(x^{2}-4\right)\left(x^{2}+2\right)}{(x+1)^{2}}0$ for $x \neq-1$, and $x^{2}+2>0$ for any $x$. Solving the inequality $x^{2}-4<0$, we find $-2<x<2$. For the final answer, we need to consider that $x \neq-1$.

Answer: $(-2,-1) \cup(-1,2)$.