\(\dfrac{x-y}{x+y-2\sqrt{xy}}\) \(\left(ĐK:x,y\ge0;x\ne y\right)\)
\(=\dfrac{\left(\sqrt{x}+\sqrt{y}\right)\left(\sqrt{x}-\sqrt{y}\right)}{\left(\sqrt{x}-\sqrt{y}\right)^2}\)
\(=\dfrac{\sqrt{x}+\sqrt{y}}{\sqrt{x}-\sqrt{y}}\)
u) (x - y)/[x + y - 2 căn(xy)]
= (x - y)/[căn(x) - căn(y)]²
= [căn(x) + căn(y)] / [căn(x) - căn(y)]