IMO 1986 LL NET60

Prove the inequality

IMO 1986 LL NET60

Origin: NET

Problem

Prove the inequality (−a+b+c)2(a−b+c)2(a+b−c)2 \geq(−a2+b2+c2)(a2−b2+c2)(a2+b2−c2) for all real numbers a, b, c.