右边是-3
a/b+a/c+b/a+b/c+c/b+c/a+3=0
(a/b+c/b+1)+(a/c+b/c+1)+(b/a+c/a+1)=0
(a+b+c)(1/b+1/c+1/a)=0
1/a+1/b+1/c不等于0
所以a+b+c=0