MathDB
Real numbers with a+b+c+d=0

Source: Kazakhstan international contest 2006, Problem 5

January 22, 2006
inequalitiescalculusinequalities proposed

Problem Statement

Let a,b,c,d a,b,c,d be real numbers with sum 0. Prove the inequality: (ab \plus{} ac \plus{} ad \plus{} bc \plus{} bd \plus{} cd)^2 \plus{} 12\geq 6(abc \plus{} abd \plus{} acd \plus{} bcd).
Back to ProblemsView on AoPS