Pascal identity:
C(n,k)=C(n-1,k-1)+C(n-1,k)
prove:
n k - th balls, consider the k-th ball, because only the k-th ball is taken and not taken to the two cases, therefore:
1. If the k is taken to the ball, the program number is C ( . 1-n-,. 1-k)
2. If the k is not taken to the ball, the program number is C (n-1, k)
sum up to give: C (n, k) = C (n-1, k- 1) + C (n-1 , k)
other:
What there is a Pascal triangle, search, I found that Pascal's Triangle, by the name of triangular matrix ...
