Home Competitions RU-ALLRUSSIAN 1985 Problem 8
RU-ALLRUSSIAN 1985 Problem 8
a 1 < a 2 < … < a n < … \mathrm{a}_{1}< \mathrm{a}_{2}< \ldots < \mathrm{a}_{\mathrm{n}}< \ldots a 1 < a 2 < … < a n < … is an unbounded sequence of positive reals. Show that there exists k such that a 1 / a 2 + a 2 / a 3 + … + a h / a h + 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 a 1 / a 2 + a 2 / a 3 + … + a h / a h + 1 < h − 1 for all h > k \mathrm{h} > \mathrm{k} h > k . Show that we can also find a k such that a 1 / a 2 + a 2 / a 3 + … + a h / a h + 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 a 1 / a 2 + a 2 / a 3 + … + a h / a h + 1 < h − 1985 for all h > k \mathrm{h} > \mathrm{k} h > k .
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