Cyclic Inequality in 4 Variables with a+b+c+d=4
Source: MEMO Individual Competition, Question 1
September 24, 2007
inequalitiesinequalities proposed
Problem Statement
Let be positive real numbers with a\plus{}b\plus{}c\plus{}d \equal{} 4.
Prove that
a^{2}bc\plus{}b^{2}cd\plus{}c^{2}da\plus{}d^{2}ab\leq 4.