Tính:
$\frac{1}{\sqrt{1}+\sqrt{3}}+\frac{1}{\sqrt{3}+\sqrt{5}}+\frac{1}{\sqrt{5}+\sqrt{7}}+...+\frac{1}{\sqrt{2009}+\sqrt{2011}}$
Tìm y:
$\frac{\sqrt{2}-1}{\sqrt{3}-\sqrt{2}}.(\frac{2}{\sqrt{2}}y-\frac{\sqrt{3}}{\sqrt{5}+1})=\frac{\sqrt{3}-2}{5+2\sqrt{3}}y-\frac{2\sqrt{3}}{\sqrt{3}-\sqrt{2}}$