设x=三次根号下(5+根号2)y=三次根号下(5-根号2)z=三次根号下5x-z=(x^3-z^3)/(x^2+xz+z^2)=sqrt(2)/(x^2+xz+z^2)z-y=(z^2-y^3)/(z^2+zy+y^2)=sqrt(2)/(z^2+zy+y^2)(x^2+xz+z^2)>(z^2+zy+y^2)故x-z...