Rút gọn biểu thức
C=\(\dfrac{x+y+2\sqrt{xy}}{\sqrt{x}+\sqrt{y}}:\dfrac{1}{\sqrt{x}-\sqrt{y}}\) (x>0; y>0; y≠0)
P=\(\left(\dfrac{2}{x-\sqrt{x}}+\dfrac{\sqrt{x}+1}{\sqrt{x}}-\dfrac{\sqrt{x}+1}{\sqrt{x}-1}\right):\dfrac{\sqrt{x}+1}{2\sqrt{x}-x}\)
D=\(\left(\dfrac{1}{\sqrt{a}+2}+\dfrac{1}{\sqrt{a}-2}\right):\dfrac{\sqrt{a}}{a-4}\) (a>0; a≠0)