Упростите выражение ((a-5)/(a+5)-(a+5)/(a-5)):5a/(25-a^2).

\[\left( \frac{a - 5^{\backslash a - 5}}{a + 5} - \frac{a + 5^{\backslash a + 5}}{a - 5} \right)\ :\frac{5a}{25 - a^{2}} =\]

\[= \frac{a^{2} - 10a + 25 - a^{2} - 10a - 25}{(a + 5)(a - 5)} \cdot \frac{25 - a^{2}}{5a} =\]

\[= \frac{- 20a\left( 25 - a^{2} \right)}{\left( a^{2} - 25 \right) \cdot 5a} = \frac{4(a^{2} - 25)}{a^{2} - 25} = 4\]