7. The solution set of the inequality $(x-2) \sqrt{x^{2}-2 x-3} \geqslant 0$ is $\qquad$ .
From $x^{2}-2 x-3=(x+1)(x-3) \geqslant 0$, we get $x \geqslant 3$ or $x \leqslant-1$.
$x \geqslant 3$ satisfies the inequality.
When $x \leqslant-1$, only $x=-1$ satisfies the inequality.