10. If the inequality about $x$
$$
\frac{x^{2}+\left(2 a^{2}+2\right) x-a^{2}+4 a-7}{x^{2}+\left(a^{2}+4 a-5\right) x-a^{2}+4 a-7}<0
$$

has a solution set that is the union of some intervals, and the sum of the lengths of these intervals is no less than 4, then the range of real number $a$ is $\qquad$
$\begin{array}{l}10 .(-\infty, 1] \cup \\ {[3,+\infty)}\end{array}$