olymmath

ISL 2016 A8

  • Answer

Determine the largest real number aa such that for all n⩾1n \geqslant 1 and for all real numbers x0,x1,…,xnx_{0}, x_{1}, \ldots, x_{n} satisfying 0=x0<x1<x2<⋯<xn0=x_{0}<x_{1}<x_{2}<\cdots<x_{n}, we have 1x1−x0+1x2−x1+⋯+1xn−xn−1⩾a(2x1+3x2+⋯+n+1xn).\frac{1}{x_{1}-x_{0}}+\frac{1}{x_{2}-x_{1}}+\cdots+\frac{1}{x_{n}-x_{n-1}} \geqslant a\left(\frac{2}{x_{1}}+\frac{3}{x_{2}}+\cdots+\frac{n+1}{x_{n}}\right) .

Dataset text NuminaMath olympiads. Quoted with source.

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\frac{4}{9}

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