Verify that $x^{3}+y^{3}+z^{3}-3xyz = \frac{1}{2}(x+y+z)[(x-y)^{2}+(y-z)^{2}+(z-x)^{2}]$

(N/A) Start with the Right Hand Side ($R$.$H$.$S$.):
$\text{R.H.S.} = \frac{1}{2}(x+y+z)[(x-y)^{2}+(y-z)^{2}+(z-x)^{2}]$
Expand the squares inside the bracket:
$= \frac{1}{2}(x+y+z)[(x^{2}-2xy+y^{2})+(y^{2}-2yz+z^{2})+(z^{2}-2zx+x^{2})]$
Combine like terms:
$= \frac{1}{2}(x+y+z)[2x^{2}+2y^{2}+2z^{2}-2xy-2yz-2zx]$
Factor out $2$ from the expression inside the square bracket:
$= \frac{1}{2}(x+y+z) \cdot 2[x^{2}+y^{2}+z^{2}-xy-yz-zx]$
$= (x+y+z)(x^{2}+y^{2}+z^{2}-xy-yz-zx)$
Using the algebraic identity $x^{3}+y^{3}+z^{3}-3xyz = (x+y+z)(x^{2}+y^{2}+z^{2}-xy-yz-zx)$,we get:
$= x^{3}+y^{3}+z^{3}-3xyz = \text{L.H.S.}$