x+y+z=m^2-np+n^2-mp+p^2-mn=1/2（2m^2-2np+2n^2-2mp+2p^2-2mn）=1/2（m^2-2mp+p^2+n^2-2np+p^2+n^2-2mn+m^2）=1/2（m-p）^2+1/2（n-p）^2+1/2（m-n）^2>=0因m,n,p是不全相等的任意实数,则x+y+z>0...