olymmath

RU-ALLRUSSIAN 1985 Problem 8

    a1<a2<…<an<…\mathrm{a}_{1}< \mathrm{a}_{2}< \ldots < \mathrm{a}_{\mathrm{n}}< \ldots is an unbounded sequence of positive reals. Show that there exists k such that a1/a2+a2/a3+…+ah/ah+1<h−1\mathrm{a}_{1} / \mathrm{a}_{2} + \mathrm{a}_{2} / \mathrm{a}_{3} + \ldots + \mathrm{a}_{\mathrm{h}} / \mathrm{a}_{\mathrm{h} + 1}< \mathrm{h} - 1 for all h>k\mathrm{h} > \mathrm{k} . Show that we can also find a k such that a1/a2+a2/a3+…+ah/ah+1<h−1985\mathrm{a}_{1} / \mathrm{a}_{2} + \mathrm{a}_{2} / \mathrm{a}_{3} + \ldots + \mathrm{a}_{\mathrm{h}} / \mathrm{a}_{\mathrm{h} + 1}< \mathrm{h} - 1985 for all h>k\mathrm{h} > \mathrm{k} .

    Dataset text NuminaMath olympiads. Quoted with source.

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