NP2 = 72, maka nilai n adalah?

NP2 = 72
n!/(n – 2)! = 72
n(n – 1)(n – 2)!/(n – 2)! = 72
n² – n = 72
n² – n – 72 = 0
(n + 8)(n – 9) = 0
ambil n > 0
maka n = 9