1/(x-y)+1/(y-z)+n/(z-x)>=0等价于 1/(x-y)+1/(y-z)>=n/(x-z)等价于(x-z)*[1/(x-y)+1/(y-z)]>=n 设 a=x-yb=y-za,b>0 则有(a+b)*(1/a+1/b)>=n 恒成立左边=(a+b)*(1/a+1/b)=2+a/b+b/a>=4等号成立当且仅...