已知a分之1+b分之1+c分之1=-2,求分式ab分之a+b+bc分之b+c+ac分之c+a的值,

a+b/ab + b+c/bc + c+a/ac
=1/b + 1/a + 1/c + 1/b + 1/a + 1/c
=2(1/a + 1/b + 1/c)
∵1/a + 1/b + 1/c=-2
∴所求=2×(-2)=-4
再问： 看补充的问题！
再答： 1/x+2 + 4x/x²-4 + 2/2-x =x-2/(x+2)(x-2) + 4x/(x+2)(x-2) -2(x+2)/(x+2)(x-2) =x-2+4x-2x-4/(x+2)(x-2) =3(x-2)/(x+2)(x-2) =3/x+2