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khaiproqn81

$S=\dfrac{1}{\sqrt{2}+\sqrt{3}}+\dfrac{1}{\sqrt{3}+\sqrt{4}}+...+\dfrac{1}{\sqrt{2005}+\sqrt{2006}} \\ S=\sqrt{3}-\sqrt{2}-\sqrt{3}+\sqrt{4}-...-\sqrt{2005}+\sqrt{2006}=\sqrt{2006}-\sqrt{2} $
 
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