(a-b)²+(b-c)²+(c-a)²>=0取最小值则a=b=c时最小值=0如求最大值展开,得 (a-b)^2+(b-c)^2+(c-a)^2 =2(a^2+b^2+c^2)-(2ab+2bc+2ca) =2(a^2+b^2+c^2)-[(a+b+c)^2-(a^2+b^2+c^2)] =3(a^2+b^2+c^2)-(a+b+c)...