

Với [tex]n\epsilon N*[/tex]
Tính [tex]S=\frac{1}{1\sqrt{2}+2\sqrt{1}}+\frac{1}{2\sqrt{3}+3\sqrt{2}}+...+\frac{1}{n\sqrt{n+1}+(n+1)\sqrt{n}}[/tex]
Tính [tex]S=\frac{1}{1\sqrt{2}+2\sqrt{1}}+\frac{1}{2\sqrt{3}+3\sqrt{2}}+...+\frac{1}{n\sqrt{n+1}+(n+1)\sqrt{n}}[/tex]