bentuk sederhana dari (x-y+z) ² dan (x+y-z) ²

(x-y+z)²+(x+y-z)²=(x-y+z)(x-y+z)+(x+y-z)
                           =x²-xy+xz-xy+y²-yz+xz-yz+z²(x+y-z)
                           =x²+y²+z²-2xy+2xz-2yz(x+y-z)
                           =x³+x²y-x²z+xy²+y³-y²z+xz²+yz²-z³-2x²y-2xy²+2xyz+2x²z+2xyz-2xz²-2xyz-2y²z+2yz²
                           =x³+y³-z³+3x²z-3y²z+3yz²-x²y-xy²-xz²+2xyz