Помогите пожалуйста!!!!!!

$\frac{a+2}{a^{2}-ab} + \frac{b-2}{b^{2}-ab}= \frac{a+2}{a(a-b)}+ \frac{b-2}{b(b-a)}= \frac{a+2}{a(a-b)}-\frac{b-2}{b(a-b)}= \\ \\ \frac{b(a+2)-a(b-2)}{ab(a-b)}= \frac{ab+2b-ab+2a}{ab(a-b)}= \frac{2(a+b)}{ab(a-b)}$

.
$\frac{8}{ a^{2}-16} - \frac{4}{ a^{2} -4a} = \frac{8}{(a-4)(a+4)}- \frac{a}{a(a-4)}= \frac{8a-a(a+4)}{a(a-4)(a+4)}= \\ \\ \frac{8a-a^{2}-4a}{a(a-4)(a+4)} = \frac{4a-a^{2} }{a(a-4)(a+4)} = \frac{a(4-a)}{-a(4-a)(a+4)}=- \frac{1}{a+4}$