1/(a^3(b+c))+1/(b^3(a+c))+1/(c^3(a+b))=(bc)^2/(ab+ac)+(ac)^2/(ab+bc)+(ab)^2/(ac+bc)>=(bc+ac+ab)^2/(2ab+2bc+2ca) //这里用柯西得到=(1/2)*(ab+bc+ac)>=(3/2)*(abc)^(2/3)//...