需要用到因式分解x^3+y^3+z^3-3xyz=(x+y+z)(x^2+y^2+z^2-xy-yz-xz)分解过程参见：(x+y+z)^2-(x^2+y^2+z^2)=2xy+2xz+2yz所以xy+xz+yz=[3*3-29]/2=-10所以3xyz=x^3+y^3+z^3-(x+y+z)(x^2+y^2+z^2-xy-yz-xz)=45-3*[29-(-10)]=-72xyz=-24
