,是什么呀?要是+的话:(1):(a+b)/(a-b)(b-c)+(b+c)/(b-c)(b-a)= [(a+b)-(b+c)]/(a-b)(b-c)=(a-c)/(a-b-)(b-c) (2):1/(a-b)(a-c)+1/(b-c)(b-a)+1/(c-a)(c-b)=[(b-c)-(a-c)+(a-b)]/(a-b)(b-c)(a-c)=0 (3)a/bx应该是a/bc吧?由题意知c=b+1=a+2;a/bc+b/ac+c/ab-1/a-1/b-1/c=[(a^2+b^2+c^2)-(ab+bc+ac)]/abc=[(a-b)^2+(b-c)^2+(a-c)^2]/2abc=(1^2+1^2+2^2)/(2*6012)=1/2004