Win_odd Dhamnekar
Junior Member
- Joined
- Aug 14, 2018
- Messages
- 207
Argue that there are exactly \(\displaystyle \binom{r}{k} \binom{n-1}{n-r+k} \) solutions of [math]x_1 + x_2 + ... + x_r = x_n[/math] for which exactly k of the \(\displaystyle x_i\) are equal to 0.
How to answer this question?
How to answer this question?