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MathNet 2007-part-02 — 187 problems (EN–VI) Question 59

Math Olympiad Vault · MathNet 2007-part-02 — 187 problems (EN–VI)

Question 59

If $x, y, z$ are positive real numbers, prove that
$$
(x+y+z)^{2}(y z+z x+x y)^{2} \leq 3\left(y^{2}+y z+z^{2}\right)\left(z^{2}+z x+x^{2}\right)\left(x^{2}+x y+y^{2}\right)
$$