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sum of 1/(√n+√(n+2))

Source: LIMIT 2019 CBS2 P10

April 28, 2021
Summationalgebra

Problem Statement

11+3+13+5+15+7++12017+2019=?\frac1{1+\sqrt3}+\frac1{\sqrt3+\sqrt5}+\frac1{\sqrt5+\sqrt7}+\ldots+\frac1{\sqrt{2017}+\sqrt{2019}}=? <spanclass=latexbold>(A)</span> 201912<span class='latex-bold'>(A)</span>~\frac{\sqrt{2019}-1}2 <spanclass=latexbold>(B)</span> 2019+12<span class='latex-bold'>(B)</span>~\frac{\sqrt{2019}+1}2 <spanclass=latexbold>(C)</span> 201914<span class='latex-bold'>(C)</span>~\frac{\sqrt{2019}-1}4 <spanclass=latexbold>(D)</span> None of the above<span class='latex-bold'>(D)</span>~\text{None of the above}