bila C(n,2)=28,maka P(n,2) adalah

Mapel : Matematika
Kelas : XII SMA
Bab : Peluang

Pembahasan :
C(n , 2) = 28
n!/(n - 2)!2! = 28
n!/(n - 2)! = 56
n(n - 1) = 56
n² - n - 56 = 0
(n - 8)(n + 7) = 0
n = 8
n = -7 (Tidak memenuhi)

P (n , 2)
= P (8 , 2)
= 8!/(8 - 2)!
= 8!/6!
= (8 x 7)
= 56

C(n,2) = 28
n! / (n-2)!2! = 28
n(n-1)(n-2)! / (n-2)!2 = 28
n(n-1) / 2 = 28
(n² - n) / 2 = 28
n² - n = 56
n² - n - 56 = 0
(n - 8)(n + 7) = 0
n = 8 atau n = -7
→ diambil yg bernilai positif (n = 8)

P(n,2) = P(8,2)
= 8! / (8-2)!
= 8! / 6!
= 8.7.6! / 6!
= 8.7 = 56