$\frac{x+1}{x-x^2}=\frac{x+1}{x(1-x)}=\frac{2(x+1)(1-x)}{2x(1-x)(1-x)}$
$=\frac{2x^2-2)}{2x(1-x)^2}$
$\frac{x+2}{2-4x+2x^2}=\frac{x+2}{2-2x-2x+2x^2}=\frac{x+2}{(2-2x)(1-x)}$
$\frac{x+2}{2(1-x)(1-x)}=\frac{x^+2x}{2x(1-x)(1-x)}$
Mẫu thức chung: $2x(1-x)(1-x)$