(i) [ab−ba]+[abba]=[a+ab+b−b+ba+a]=[2a2b02a]
(ii) [a2+b2b2+c2a2+c2a2+b2]+[2ab2bc−2ac−2ab]
=[a2+b2+2abb2+c2+2bca2+c2−2aca2+b2−2ab]
=[(a+b)2(b+c)2(a−c)2(a−b)2]
(iii) ⎡⎢⎣−182458−6165⎤⎥⎦+⎡⎢⎣1283702654⎤⎥⎦
=⎡⎢⎣−1+128+82+34+75+08+2−6+616+55+4⎤⎥⎦
=⎡⎢⎣11165115100219⎤⎥⎦
(iv) [cos2xsin2xsin2xcos2x]+[sin2xcos2xcos2xsin2x]
=[1111](∵sin2x+cos2x=1)