4.a,b,c為不相等的實數，a2 + b2 + abx = b2 + c2 + bcx = c2 + a2 + cax ，則下列選項何者正確？(A)有x = -2的解 (B)x =1時必有a + b + c = 0 (C)a + b + c = 0時有x =1的解(D)a + b + c ≠ 0時x = -2 (E)a + b + c = 0時x為任意實數；a + b + c ≠ 0時x = -2 。