求解此问题

x*x*x*x（y-z)+y*y*y*y(z-x)+z*z*z*z(x-y)
=x*x*x*x（y-z)+y*y*y*y(z-x)+z*z*z*z[(x-z)+(z-y)]
=(x^4-z^4)(y-z)+(y^4-z^4)(z-x)
=(x-z)(y-z)(xxx+xxz+xzz+zzz)+(y-z)(z-x)(yyy+yyz+yzz+zzz)
=(x-z)(y-z)(xxx+xxz+xzz-yyy-yyz-yzz)
=(x-z)(y-z)(x-y)[ (xx+xy+yy)+z(x+y)+zz ]
=(x-z)(y-z)(x-y)(x^2+y^2+z^2+xz+xy+yz)

(y+z)(y+z)+(z+x)(z+x)+(x+y)(x+y)
=2(x^2+y^2+z^2+xz+xy+yz)

所以
[x*x*x*x（y-z)+y*y*y*y(z-x)+z*z*z*z(x-y)] /[(y+z)(y+z)+(z+x)(z+x)+(x+y)(x+y) ]
=-0.5(y-z)(z-x)(x-y)