Giải thích các bước giải:
$\left(\dfrac{x}{x^2-25}-\dfrac{x-5}{x^2+5x}\right):\left(\dfrac{2x-5}{x^2+5x}+\dfrac{x}{5-x}\right)$
$=\left(\dfrac{x}{(x-5)(x+5)}-\dfrac{x-5}{x(x+5)}\right):\left(\dfrac{2x-5}{x(x+5)}-\dfrac{x}{x-5}\right)$
$=\left(\dfrac{x^2}{x(x-5)(x+5)}-\dfrac{(x-5)^2}{x(x-5)(x+5)}\right):\left(\dfrac{(x-5)(2x-5)}{x(x-5)(x+5)}-\dfrac{x^2(x+5)}{x(x-5)(x+5)}\right)$
$=\left(\dfrac{x^2-(x-5)^2}{x(x-5)(x+5)}\right):\left(\dfrac{(x-5)(2x-5)-x^2(x+5)}{x(x-5)(x+5)}\right)$
$=\left(\dfrac{10x-25}{x(x-5)(x+5)}\right):\left(\dfrac{-x^3-3x^2-15x+25}{x(x-5)(x+5)}\right)$
$=\dfrac{10x-25}{x(x-5)(x+5)}.\dfrac{x(x-5)(x+5)}{-x^3-3x^2-15x+25}$
$=\dfrac{10x-25}{-x^3-3x^2-15x+25}$
