2006 IMO Problems/Problem 3

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Problem

Determine the least real number $M$ such that the inequality \[\left| ab\left(a^{2}-b^{2}\right)+bc\left(b^{2}-c^{2}\right)+ca\left(c^{2}-a^{2}\right)\right|\leq M\left(a^{2}+b^{2}+c^{2}\right)^{2}\] holds for all real numbers $a,b$ and $c$

Solution

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