`Q=(x\sqrt{y}-y\sqrt{x})/(x-2\sqrt{xy}+y)` `(x,y>=0,xney)`
`Q=(\sqrt{xy}.(\sqrt{x}-\sqrt{y}))/((\sqrt{x}-\sqrt{y})^2)`
`Q=(\sqrt{xy})/(\sqrt{x}-\sqrt{y})`
b) Sửa đề
`P=(a+4\sqrt{a}+4)/(2+\sqrt{a})+(4-a)/(\sqrt{a}-2)` `(a>=0,ane4)`
`P=((\sqrt{a}+2)^2)/(2+\sqrt{a))-((\sqrt{a}-2)(\sqrt{a}+2))/(\sqrt{a}-2)`
`P=\sqrt{a}+2-\sqrt{a}-2`
`P=0`