olymmath

APMO 2018 Problem 2

  • Paper

Let f(x)f(x) and g(x)g(x) be given by

f(x)=1x+1x−2+1x−4+⋯+1x−2018f(x)=\frac{1}{x}+\frac{1}{x-2}+\frac{1}{x-4}+\cdots+\frac{1}{x-2018}

and

g(x)=1x−1+1x−3+1x−5+⋯+1x−2017.g(x)=\frac{1}{x-1}+\frac{1}{x-3}+\frac{1}{x-5}+\cdots+\frac{1}{x-2017} .

Prove that

∣f(x)−g(x)∣>2|f(x)-g(x)|>2

for any non-integer real number xx satisfying 0<x<20180<x<2018.

Dataset text NuminaMath olympiads. Quoted with source.

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