Помогите срочно пж прошу

Решите задачу:

$\frac{(a - 5)^2}{a^2 + 5a} : \left( \frac{5}{a + 5} - \frac{a^2 + 25}{a^2 - 25} - \frac{5}{5 - a} \right) = \frac{(a - 5)^2}{a(a + 5)} : \left( \frac{5}{a + 5} - \frac{a^2 + 25}{(a - 5)(a + 5)} + \frac{5}{a - 5} \right) = \frac{(a - 5)^2}{a(a + 5)} : \left( \frac{5a - 25 - a^2 - 25 + 5a + 25}{(a - 5)(a + 5)} \right) = \frac{(a - 5)^2}{a(a + 5)} : \left(-\frac{a^2 - 10a + 25}{(a - 5)(a + 5)} \right) = - \frac{(a - 5)^2 (a - 5)(a + 5)}{a(a + 5)(a - 5)^2} = -\frac{a - 5}{a}$