i. Here, a = 2m and b = 5
(2m – 5)3 = (2m)3 – 3(2m)2 (5) + 3(2m) (5)2 – (5)3 … [(a – b)3 = a3 – 3a2b + 3ab2 – b3]
= 8m3 – 3(4m2)(5) + 3(2m)(25) – 125
= 8m3 – 60m2 + 150m – 125
ii. Here, a = 4 and b = p
(4 – p)3 = (4)3 – 3(4)2(p) + 3(4)(p)2 – (p)3 … [(a – b)3 = a3 – 3a2b + 3ab2 – b3]
= 64 – 3(16)(p) + 3(4)(p2) – p3 = 64 – 48p + 12p2 – p3
iii. Here, a = 7x and b = 9y
(7x – 9y)3 = (7x)3 – 3(7x)2 (9y) + 3 (7x)(9y)2 – (9y)3 …[(a – b)3 = a3 – 3a2b + 3ab2 – b3]
= 343x3 – 3(49x2)(9y) + 3(7x)(81y2) – 729y3
= 343x3 – 1323x2y + 1701xy2 – 729y3
iv. (58)3 = (60 – 2)3
Here, a = 60 and b = 2
(58)3 = (60)3 – 3(60)2(2) + 3(60)(2)2 – (2)3 … [(a – b)3 = a3 – 3a2b + 3ab2 – b3]
= 216000 – 3(3600)(2) + 3(60)(4) – 8
= 216000 – 21600 + 720 – 8 =195112
v. (198)3 = (200 – 2)3
Here, a = 200 and b = 2
(198)3 = (200)3 – 3(200)2(2) + 3(200)(2)2 – (2)3 … [(a – b)3 = a3 – 3a2b + 3ab2 – b3]
= 8000000 – 3(40000)(2) + 3(200)(4) – 8
= 8000000 – 240000 + 2400 – 8 = 7762392
vi. Here, a = 2p and b = 1/2p
vii. Here, A = 1 and B = 1/a
viii. Here, a = x/3 and b = 3/x