- #1
Jef123
- 29
- 0
1. How do you get n!/(k-1)!(n-k+1)! from [tex]
\begin{pmatrix}
n\\k-1
\end{pmatrix}
[/tex]
I thought it would be n!/(k-1)!(n-k-1)! where the n-k+1 on the bottom of the fraction would be a n-k-1 instead. I don't understand why there is a "+1" wouldn't you just replace k with k-1 in the binomial formula?
\begin{pmatrix}
n\\k-1
\end{pmatrix}
[/tex]
I thought it would be n!/(k-1)!(n-k-1)! where the n-k+1 on the bottom of the fraction would be a n-k-1 instead. I don't understand why there is a "+1" wouldn't you just replace k with k-1 in the binomial formula?