Bounding 1+2++n\sqrt{1} + \sqrt{2} + \cdots + \sqrt{n}

7/10Inductioninequality

Problem

Prove that for every positive integer nn,

2n3n  <  k=1nk  <  4n+36n.\frac{2n}{3}\sqrt{n} \;<\; \sum_{k=1}^{n} \sqrt{k} \;<\; \frac{4n+3}{6}\sqrt{n}.

Answer

Solution

Difficulty7/10
TopicsInduction, inequality

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