\[y = f(x);\ \ f(x) = \sqrt{x};\ \ f(x - 5)\]
\[x = \left( \frac{1}{2 - \sqrt{3}} + \frac{1}{2 + \sqrt{3}} \right) \cdot \sqrt{75}\]
\[\left( \frac{1}{2 - \sqrt{3}} - \frac{1}{2 + \sqrt{3}} \right) \cdot \sqrt{75} =\]
\[= \frac{2 + \sqrt{3} - 2 + \sqrt{3}}{\left( 2 - \sqrt{3} \right)\left( 2 + \sqrt{3} \right)} \cdot \sqrt{75} =\]
\[= \frac{2\sqrt{3}}{4 - 3} \cdot 5\sqrt{3} = 30\]
\[f(30 - 5) = f(25)\]
\[\sqrt{25} = 5\]
\[Ответ:5.\ \]