\[\frac{2mn}{n^{2} - m^{2}} \cdot \left( \frac{1^{\backslash n}}{m} - \frac{1^{\backslash m}}{n} \right) =\]
\[= \frac{2mn}{(n - m)(n + m)} \cdot \frac{n - m}{\text{nm}} =\]
\[= \frac{2}{n + m}\]
\[m = \sqrt{3} + 6;\ \ n = \sqrt{\left( \sqrt{3} - 2 \right)^{2}}:\]
\[\frac{2}{\left| \sqrt{3} - 2 \right| + \sqrt{3} + 6} = \frac{2}{2 - \sqrt{3} + \sqrt{3} + 6} =\]
\[= \frac{2}{8} = \frac{1}{4} = 0,25.\]
\[Ответ:0,25.\]