n-1Cn-1

n-1Cn-1 is equal to 1.

Explanation:

n-1Cn-1 can be rewritten as (n-1)! / [(n-1-(n-1))! * (n-1)!] = (n-1)! / [0! * (n-1)!] = (n-1)! / 1 = (n-1)

Since (n-1) is a constant, n-1Cn-1 is always equal to 1.