1 votes 1 votes Prove the hockeystick identity $\displaystyle{}\sum_{k=0}^{r} \binom{n + k}{k} = \binom{n + r + 1}{r}$ whenever $n$ and $r$ are positive integers, using a combinatorial argument. using Pascal’s identity. Combinatory kenneth-rosen discrete-mathematics counting binomial-theorem descriptive + – admin asked Apr 30, 2020 admin 255 views answer comment Share Follow See all 0 reply Please log in or register to add a comment.