紧急!一道初二分式计算题 已知abc=1,求(a/ab+a+1)+(b/bc+b+1)+(c/ac+c+1)的值．

已知abc=1.求a/(ab+a+1)+b/(bc+b+1)+c/(ac+c+1)的值.
原式= a/(ab+a+abc)+b/(bc+b+1)+c/(ac+c+1)
=1/(b+1+bc)+b/(bc+b+1)+c/(ac+c+1)········ ·分子分母约去a
=(1+b)/(b+1+bc)+c/(ac+c+1) ············前两项相加
=(1+b)/(b+1+bc)+c/(ac+c+abc) ···········后一项括号中的1换成abc；
=(1+b)/(b+1+bc)+1/(a+1+ab) ············约去c
=(1+b)/(b+1+bc)+abc/(a+abc+ab) ··········约去a
=(1+b)/(b+1+bc)+bc/(1+bc+b)
=(1+b+bc)/(1+bc+b)
=1
其实这就是把1不停的换,换成分母相同的再加