1. The problem statement, all variables and given/known data Prove: xyzw[tex]\geq x+y+z+w-3[/tex],where [tex]x\geq 1,y\geq 1,z\geq 1,w\geq 1[/tex] 2. Relevant equations 3. The attempt at a solution The only thing i could try is to square both sides but then this leads nowhere. Any ideas??