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MathNet 2014 Question 63

Math Olympiad Vault · MathNet 2014

Question 63

Given positive real numbers $a$, $b$, $c$, with $ab + bc + ca \ge a + b + c$, prove that

$$(a+b+c)(ab+bc+ca) + 3abc \ge 4(ab+bc+ca).$$

(I. Gorodnin)