Ta có:\(\dfrac{x-2\sqrt{xy}+y}{\sqrt{x}-\sqrt{y}}-\dfrac{x-y}{\sqrt{x}+\sqrt{y}}\)
\(=\dfrac{\left(\sqrt{x}-\sqrt{y}\right)^2}{\sqrt{x}-\sqrt{y}}-\dfrac{\left(\sqrt{x}-\sqrt{y}\right)\left(\sqrt{x}+\sqrt{y}\right)}{\sqrt{x}+\sqrt{y}}\)
\(=\sqrt{x}-\sqrt{y}-\sqrt{x}+\sqrt{y}=0\)
\(\dfrac{x-2\sqrt{xy}+y}{\sqrt{x}-\sqrt{y}}-\dfrac{x-y}{\sqrt{x}+\sqrt{y}}\)
= \(\dfrac{(\sqrt{x}-\sqrt{y})^2}{\sqrt{x}-\sqrt{y}}-\dfrac{(\sqrt{x}-\sqrt{y})(\sqrt{x}+\sqrt{y})}{\sqrt{x}+\sqrt{y}}\)
=\((\sqrt{x}-\sqrt{y})(\sqrt{x}-\sqrt{y})\)
=\((\sqrt{x}-\sqrt{y})^2\)
= \(x-2\sqrt{xy}+y\)