Question 1201548
n = 11.
you get p(n,2) = n! / (n-x)! = 11! / 9! = 11 * 10 * 9! / 9! = 11 * 10 = 110.
the simple rule is:
p(n,1) = n
p(n,2) = n * (n-1)]
p(n,3) = n * (n-1) * (n-2)
p(n,4) = n * (n-1) * (n-2) * n-3)
etc.
if n is 11, then:
p(11,1) = 11
p(11,2) = 11 * 10 = 110
p(11,3) = 11 * 10 * 9 = 990
p(11,4) = 11 * 10 * 9 * 8 = 7920
etc.....
looking at p(11,4), you get:
p(11,4) = 11! / (11-4)! = 11! / 7! = 11 * 10 * 9 * 8 * 7! / 7! = 11 * 10 * 9 * 8 = 7920.