Pₙ = n!
Aₐᵇ = a!/(a - b)!
A₇⁵ - P₅ = 7! / (7 - 5)! - 5! = 7!/2! - 1*2*3*4*5 = 3*4*5*6*7 - 4*5*6 = 120*(21 - 1) = 120*20 = 2400
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Pₙ = n!
Aₐᵇ = a!/(a - b)!
A₇⁵ - P₅ = 7! / (7 - 5)! - 5! = 7!/2! - 1*2*3*4*5 = 3*4*5*6*7 - 4*5*6 = 120*(21 - 1) = 120*20 = 2400