解a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)+3=a/b+a/c+b/c+b/a+c/a+c/b+3=(a+c)/b+(a+b)/c+(b+c)/c+3=-b/b-c/c-a/a+3=-1-1-1+3=0
