左边=1/abc-(1/ab+1/bc+1/ca)+(1/a+1/b+1/c)-1
=1/abc-(a+b+c)/abc+(1/a+1/b+1/c)-1
=1/a+1/b+1/c-1
不是 1/abc - 1
不好意思你算错了..
然后可以9