Сократите дробь: (9-a)/(корень из a-3).

Ответ:

\[\ \frac{9 - a}{\sqrt{a} - 3} = \frac{\left( 3 - \sqrt{a} \right)\left( 3 + \sqrt{a} \right)}{\sqrt{a} - 3} =\]

\[= - \left( 3 + \sqrt{a} \right)\ \]

\[\frac{3}{2\sqrt{7} + 1} - \frac{3}{2\sqrt{7} - 1} =\]

\[= \frac{3 \cdot \left( 2\sqrt{7} - 1 \right) - 3 \cdot \left( 2\sqrt{7} + 1 \right)}{28 - 1} =\]

\[= \frac{6\sqrt{7} - 3 - 6\sqrt{7} - 3}{27} = \frac{- 6}{27} = - \frac{2}{9}.\]

\[\ 3\sqrt{1\frac{11}{25}} - 1 = 3\sqrt{\frac{36}{25}} - 1 = 3 \cdot \frac{6}{5} - 1 =\]

\[= 3\frac{3}{5} - 1 = 2\frac{3}{5}\]