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Prove that xyz+(1-x)(1-y)(1-z) ≤ 1 [Slovenia 2010]

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November 14, 2010
probabilityfunctioninequalitiesinequalities proposed

Problem Statement

Let x,yx,y and zz be real numbers such that 0x,y,z1.0 \leq x,y,z \leq 1. Prove that xyz+(1x)(1y)(1z)1.xyz+(1-x)(1-y)(1-z) \leq 1. When does equality hold?