(i) (A+B)2=A2+AB+BA+B2≠A2+2AB+B2 in general.(A+B)^2=A^2+AB+BA+B^2\ne A^2+2AB+B^2\ \text{in general.}(A+B)2=A2+AB+BA+B2=A2+2AB+B2 in general.