\[\boxed{\mathbf{798\ (798).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1.\frac{1}{(a - 1)(a + 1)} + \frac{1}{(a - 1)^{2}} =\]
\[= \frac{a - 1 + a + 1}{(a - 1)^{2}(a + 1)} =\]
\[= \frac{2a}{(a - 1)^{2}(a + 1)}\]
\[2.\frac{(a - 1)^{2} \cdot 2a}{(a - 1)^{2}(a + 1)} = \frac{2a}{a + 1}\]
\[3.\frac{2a}{a + 1} + \frac{2}{a + 1} = \frac{2a + 2}{a + 1} =\]
\[= \frac{2 \cdot (a + 1)}{a + 1} = 2\ \]
\[Ответ:\ верно.\]