tentukan nilai n persamaan (n+2)!/(n-1)=42n

(n+2)!/(n-1)! = 42 n
(n+2)(n+1)(n)(n-1)!/(n-1)! = 42 n
(n+2)(n+1)n = 42 n
(n+2)(n+1) = 42
n² + 3n + 2 = 42
n² + 3n - 40 = 0
(n + 8)(n - 5) = 0
n = -8 v n = 5
yang dipilih yang positif
jadi n = 5