1. Given $f(x)=-\log _{3}\left(x^{2}-a x-a\right)$ is monotonically increasing on $(-\infty, 1-\sqrt{3})$. Then the range of values for $a$ is $\qquad$ .
$$
-1.2-2 \sqrt{3} \leqslant a \leqslant 2 \text {. }
$$

Since $y=\log _{3}\left(x^{2}-a x-a\right)$ is monotonically decreasing on $(-\infty, 1-\sqrt{3})$, we have:
$$
\left\{\begin{array}{l}
x_{0}=\frac{a}{2} \geqslant 1-\sqrt{3}, \\
(1-\sqrt{3})^{2}-a(1-\sqrt{3})-a \geqslant 0 .
\end{array}\right.
$$

Solving this, we get $2-2 \sqrt{3} \leqslant a \leqslant 2$.