i. Here, a = x and b = 5

(x – 5)(x + 5) = (x)^{2} – (5)^{2} …. [(a + b)(a – b) = a^{2} – b^{2} ]

= x^{2} – 25

ii. Here, A = 2a and B = 13

(2a – 13)(2a + 13) = (2a)^{2} – (13)^{2} …. [(A + B)(A – B) = A^{2} – B^{2} ]

= 4a^{2} – 169

iii. Here, a = 4z and b = 5y

(4z – 5y)(4z + 5y) = (4z)^{2} – (5y)^{2} …. [(a + b)(a – b) = a^{2} – b^{2} ]

= 16z^{2} – 25y^{2}

iv. Here, a = 2t and b = 5

(2t – 5)(2t + 5) = (2t)^{2} – (5)^{2} …. [(a + b)(a – b) = a^{2} – b^{2} ]

= 4t^{2} – 25