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