Rút gọn biểu thức:
$C=\frac{2+\sqrt{3}}{\sqrt{2}+\sqrt{2+\sqrt{3}}}+\frac{2-\sqrt{3}}{\sqrt{2}-\sqrt{2-\sqrt{3}}}$
$D=\frac{\sqrt{2}+\sqrt{3}+\sqrt{4}}{\sqrt{2}+\sqrt{3}+\sqrt{6}+\sqrt{8}+\sqrt{16}}$
$E=\frac{1+\frac{\sqrt{3}}{2}}{1+\sqrt{1}+\frac{\sqrt{3}}{2}}+\frac{1-\frac{\sqrt{3}}{2}}{1-\sqrt{\frac{\sqrt{3}}{2}}}$
$F=\sqrt{x+2\sqrt{2x-4}} + \sqrt{x-2\sqrt{2x-4}}$
$G=\sqrt{a+b+c+2\sqrt{ac+bc}}+\sqrt{a+b+c-2\sqrt{ac+bc}}$
$H=\sqrt{x-\sqrt{x^{2}-4x+4}}$