i. Here, a = x and b = 5
(x – 5)(x + 5) = (x)2 – (5)2 …. [(a + b)(a – b) = a2 – b2 ]
= x2 – 25
ii. Here, A = 2a and B = 13
(2a – 13)(2a + 13) = (2a)2 – (13)2 …. [(A + B)(A – B) = A2 – B2 ]
= 4a2 – 169
iii. Here, a = 4z and b = 5y
(4z – 5y)(4z + 5y) = (4z)2 – (5y)2 …. [(a + b)(a – b) = a2 – b2 ]
= 16z2 – 25y2
iv. Here, a = 2t and b = 5
(2t – 5)(2t + 5) = (2t)2 – (5)2 …. [(a + b)(a – b) = a2 – b2 ]
= 4t2 – 25