X+Y+Z=0,问X的三次方+Y的三次方+Z的三次方=?（已知答案为3XYZ)要解题步骤

X的三次方+Y的三次方+Z的三次方=（x+y）（x2-xy+y2）+Z的三次方=-z（x2-xy+y2）+Z的三次方（x+y=-z）=-z（x2-xy+y2-z2）=-z[x（x-y）+(y+z)(y-z)]=-z[x(x-y)-x(y-z)] (y+z=-x)=-z[x(x-y-y+z)]=-zx(x+z-2y)=-zx(-y-2y...