(i) (7x + 2y)2 = (7x)2 + 2 (7x) (2y) + (2y)2 = 49x2 + 28xy + 4y2
(ii) (4m – 3m)2 = (4m)2 – 2(4m) (3m) + (3m)2 = 16m2 – 24mn + 9n2
(iii) (4a + 3b) (4a – 3b) [We have (a + b) (a – b) = a2 – b2]
Put [a = 4a, b = 3b]
(4a + 3b) (4a – 3b) = (4a)2 – (3b)2 = 16a2 – 9b2
(iv) (k + 2)(k – 3) [We have (x + a) (x – b) = x2 + (a – b)x – ab]
Put [x = k, a = 2, b = 3]
(k + 2) (k – 3) = k2 + (2 – 3)x – 2 x 3 = k2 – x – 6