▪ Ανισότητες - 140η

Aν $x,y,z>0$, να αποδειχθεί ότι

$\frac{(x+y+z{)}^3-2(x+y+z)(x^2+y^2+z^2)}{xyz}\le 9$.

Proposed by Neculai Stanciu, George Emil Palade Secondary School, Buzau,Romania