一
已知abc=0,求 的值
已知abc=1
则a/(ab+a+1)+b/(bc+b+1)+c/(ac+c+1)
=a/(ab+a+1)+ab/(abc+ab+a)+abc/(a^2*bc+abc+ab)
=a/(ab+a+1)+ab/(ab+a+1)+1/(ab+a+1)
=(ab+a+1)/(ab+a+1)
=1