12 nP3 = 7 (n-1) P4, nilai n =

jawab

12 ( nP3) = 7 { (n-1) P4 }
12 .n ! / (n-3)!  =  7 (n-1) ! / (n-1 -4)!
12 , n! / (n-3)! =  7  (n-1) ! / (n - 5 ) !
12 n! / (n- 1) ! =  7 (n-3)! / (n-5)!
12 n (n-1) ! / (n-1)!   = 7  (n-3)(n-4)(n-5)! /(n-5)!
12 n= 7(n-3)(n-4)
12 n = 7 (n² -7n +12)
12 n = 7n² -49 n + 84
7n² - 49 n -12 n  + 84 = 0
7n² - 61 n + 84 = 0
(7n - 12)(n -7) = 0
7n - 12 = 0  atau n - 7 = 0
n = 12/7  atau n = 7
n bilangan bulat , maka n  = 7