Question

solve for n if P(n,3)=2c(n,2), n{N

Answer 1

P(n,3)=2c(n,2)

n!/(n-3)! = 2 x n!/(2!(n-2)!) , use def of n! to reduce to
n(n-1)(n-2) = n(n-1) , divide by n(n-1)
n-2 = 1
n = 3

check P(3,3) = 3x2x1 = 6
2C(3,2) = 2(3) = 6