Let x,y,zx, y, zx,y,z be three positive reals such that xyz≥1xyz \geq 1xyz≥1. Prove that x5−x2x5+y2+z2+y5−y2x2+y5+z2+z5−z2x2+y2+z5≥0.\frac{x^5 - x^2}{x^5 + y^2 + z^2} + \frac{y^5 - y^2}{x^2 + y^5 + z^2} + \frac{z^5 - z^2}{x^2 + y^2 + z^5} \geq 0.x5+y2+z2x5−x2+x2+y5+z2y5−y2+x2+y2+z5z5−z2≥0.