.题目应是若a.b.c两两不相等,求(2a-b-c)/(a方-ab-ac+bc)+(2b-c-a)/(b方-ab-bc+ac)+(2c-a-b)/(c方-ac-bc+ab)的值
(2a-b-c)/(a方-ab-ac+ab)+(2b-c-a)/(b方-ab-bc+ac)+(2c-a-b)/(c方-ac-bc+ab)的值
=(2a-b-c)/(a-b)(a-c)+(2b-c-a)/(b-a)(b-c)+(2c-a-b)/(c-a)(c-b)
=〔(a-b)+(a-c)〕/(a-b)(a-c)+〔(b-c)+(b-a)〕/(b-a)(b-c)+〔(c-a)+(c-b)〕/(c-a)(c-b)
=1/(a-c)+1/(a-b)+1/(b-a)+1/(b-c)+1/(c-b)+1/(c-a)
=1/(a-c)+1/(a-b)-1/(a-b)+1/(b-c)-1/(b-c)-1/(a-c)
=0
少条件吧