2. Given $a-b=5+\sqrt{6}, b-c=5-$ $\sqrt{6}$. Then $a^{2}+b^{2}+c^{2}-a b-b c-c a=$.
2. Given, we have $a-c=10$. Then
$$
\begin{array}{l}
a^{2}+b^{2}+c^{2}-a b-b c-c a \\
=\frac{1}{2}\left[(a-b)^{2}+(b-c)^{2}+(c-a)^{2}\right]=\underline{81} .
\end{array}
$$