Сократите дробь: (25-b)/(корень из b+5).

\[\ \frac{25 - b}{\sqrt{b} + 5} = \frac{\left( 5 - \sqrt{b} \right)\left( 5 + \sqrt{b} \right)}{\sqrt{b} + 5} = 5 - \sqrt{b}\]

\[\frac{4}{3 + \sqrt{15}} + \frac{4}{3 - \sqrt{15}} =\]

\[= \frac{4 \cdot \left( 3 - \sqrt{15} \right) + 4 \cdot \left( 3 + \sqrt{15} \right)}{9 - 15} =\]

\[= \frac{12 - 4\sqrt{15} + 12 + 4\sqrt{15}}{- 6} = \frac{24}{- 6} = - 4.\]

\[\ 14x^{2} - 9x = 0\]

\[x(14x - 9) = 0\]

\[x = 0\ \ \ \ \ \ \ \ \ \ \ 14x - 9 = 0\]

\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 14x = 9\]

\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = \frac{9}{14}\]

\[Ответ:\ \ \ x = 0\ \ \ и\ \ x = \frac{9}{14}.\]