(i) 16x5 − 144x3
= 16x3(x2 − 9)
= 16 x3 [(x)2 − (3)2]
= 16 x3(x − 3) (x + 3) [a2 − b2 = (a − b) (a + b)]
(ii) (l + m)2 − (l − m)2
= [(l + m) − (l − m)] [(l + m) + (l − m)]
[Using identity a2 − b2 = (a − b) (a + b)]
= (l + m − l + m) (l + m + l − m)
= 2m × 2l
= 4ml
= 4lm
(iii) 9x2y2 − 16 = (3xy)2 − (4)2
= (3xy − 4) (3xy + 4) [a2 − b2 = (a − b) (a + b)]
