Questão 2132350

\(\sum_{k=0}^{r}\begin{pmatrix}n\\k\end{pmatrix}\begin{pmatrix}m\\r-k\end{pmatrix}\)

\(\sum_{k=0}^{r}\begin{pmatrix}m\\k\end{pmatrix}\begin{pmatrix}m\\r-k\end{pmatrix}\)

\(\sum_{k=0}^{r}\begin{pmatrix}n\\k\end{pmatrix}\begin{pmatrix}m\\r\end{pmatrix}\)

\(\sum_{k=0}^{r}\begin{pmatrix}n\\k\end{pmatrix}\begin{pmatrix}n\\r-k\end{pmatrix}\)

\(\sum_{k=0}^{r}\begin{pmatrix}n\\k\end{pmatrix}\begin{pmatrix}m\\k\end{pmatrix}\)