(i) (232). (251)
= (232+51)
= ((2)1510+3)
= ((2)1513)
Hence, (232). (251) = ((2)1513)
(ii) (331)7
=(331)7=(33×717)=(3211)
Hence, (331)7=(3211)
(iii) 11411121
= (1121−41)
= (1142−1)
= (1141)
Hence, 11411121 = (1141)
(iv) (721). (821)
=(7×8)21[∵am×bm=(ab)m]=5621
Hence, (721).(821)=5621