Помогите решить! Пожалуйста!

1) $\frac{x-5}{x^2+5x}+\frac{x+5}{x^2-5x}-\frac{4x}{x^2+25}=\frac{x-5}{x(x+5)}+\frac{x+5}{x(x-5)}-\frac{4x}{(x+5)(x-5)}=$
$\frac{(x-5)^2}{x(x+5)(x-5)}+\frac{(x+5)^2}{x(x-5)(x+5)}-\frac{4x^2}{x(x+5)(x-5)}=$
= $\frac{(x-5)^2+(x+5)^2-4x^2}{x(x+5)(x-5)}=\frac{(x^2-10x+25+x^2+10x+25-4x^2}{x(x+5)(x-5)}=\frac{50-2x^2}{x(x^2-25)}$
$=\frac{2(25-x^2)}{x(x^2-25)}=- \frac{2}{x}$

2) $\frac{x-81}{9x-81} - \frac{7x+9}{9x-x^2}=$
$\frac{x-81}{9(x-9)} - \frac{7x+9}{x(9-x)}=$
$\frac{x-81}{9(x-9)} + \frac{7x+9}{x(x-9)}=\frac{x-81+7x+9}{x(x-9)}=$
$=\frac{8x-72}{x(x-9)}=\frac{8(x-9)}{x(x-9)}= \frac{8}{x}$