Сгруппируем: (x-y)(xy-xz)+(y-z)(yz-xz)=x(x-y)(y-z)+z(y-z)(y-x)=x(x-y)(y-z)-z(y-z)(x-y)=(x-y)(y-z)(x-z)
Сгруппируем: (x-y)(xy-xz)+(y-z)(yz-xz)=x(x-y)(y-z)+z(y-z)(y-x)=x(x-y)(y-z)-z(y-z)(x-y)=(x-y)(y-z)(x-z)