题目抄错了吧是不是这个:X/(1+A+AB)+X/(1+B+BC)+X/(1+C+AC)=2009 因为 ABC = 1,所以:1 + B + BC = ABC + B + BC = B(AC+1+C)=B (1 + C + AC)···①1 + A + AB = ABC + A + AB =A(BC+1+B)= A (1 + B + BC)(1再换成ABC) = AB (1 + C + AC)···②所以:原式左边=X/(1 + A + AB) + X/(1 + B + BC) + X/(1 + C + AC)= X/[AB(1 + C + AC)] + X/[B(1 + C + AC)] + X/(1 + C + A