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Inequality from JMO 2010

Source: 2010 Japan Mathematical Olympiad Finals, Problem 4

February 11, 2010
inequalitiesinequalities proposed

Problem Statement

Let x, y, z x,\ y,\ z be positive real numbers. Prove that \frac {1 \plus{} yz \plus{} zx}{(1 \plus{} x \plus{} y)^2} \plus{} \frac {1 \plus{} zx \plus{} xy}{(1 \plus{} y \plus{} z)^2} \plus{} \frac {1 \plus{} xy \plus{} yz}{(1 \plus{} z \plus{} x)^2}\geq 1