Formula of X^3+y^3+z^3-3xyz

The formula of X^3+y^3+z^3-3xyz is (x+y+z)(x2+y2+z2−xy−yz−zx). Proof of x3+y3+z3−3xyz=(x+y+z)(x2+y2+z2−xy−yz−zx) x3+y3+z3−3xyz=(x+y+z)(x2+y2+z2−xy−yz−zx) Assume L.H.S=x3+y3+z3−3xyz and