Question

Bantu jawab ka sekarang

Answer 1

A) n! /(n - 1) = 10
    n.(n - 1)! / (n - 1)! = 10
     n = 10
b) (n + 1)! / n! = 21
    (n + 1) n! / n! = 21
     n + 1 = 21
           n = 21 - 1
           n = 20
c) (n - 1)! / (n - 3)! = 30
    (n - 1)(n - 2) (n - 3)! / (n - 3)! = 30
     (n - 1)(n - 2) = 30
     n^2 - 3n + 2 = 30
     n^2 - 3n + 2 - 30 = 0
     n^2 - 3n - 28 = 0
     (n - 7) (n + 4) = 0
     n - 7 = 0   atau n + 4 = 0
     n = 7  atau n = - 4 (tak memenuhi