Упростите выражение: ((9\ х-4) - х-4) : (х2 - 10х + 25\ 4х) =

Решите задачу:

$(\frac{9}{x-4}-x-4):\frac{x^2-10x+25}{4x}= \frac{9-(x-4)(x+4)}{x-4}:\frac{x^2-2*5x+5^2}{4x}= \\ =\frac{9-x^2+16}{x-4}:\frac{(x-5)^2}{4x}=\frac{25-x^2}{x-4}:\frac{(x-5)^2}{4x}=\frac{(5-x)(5+x)}{x-4}*\frac{4x}{(x-5)^2}= \\ =\frac{-(x-5)(5+x)}{x-4}*\frac{4x}{(x-5)^2}= \frac{-4x(5+x)}{(x-4)(x-5)}$