$$
\begin{array}{l}
\text { 2. Compare the sizes: } \frac{1}{2}(\sqrt{1998}-\sqrt{2000}) \\
\sqrt{1998}-\sqrt{1999} .
\end{array}
$$
3. Given that $\alpha$ is a root of the equation $x^{2}-3 x-1=0$. Then $\alpha^{6}+120 \alpha^{-2}=$ $\qquad$ .
Answer: >Answer:1309