Bezeichne \( \left(\begin{array}{c}n \\ k_{1}, k_{2}, \ldots, k_{\ell}\end{array}\right) \) der Multinomialkoeffizient. Zeigen Sie, dass
\( \left(\begin{array}{c} n+1 \\ k_{1}, k_{2}, \ldots, k_{\ell} \end{array}\right)=\left(\begin{array}{c} n \\ k_{1}-1, k_{2}, \ldots, k_{\ell} \end{array}\right)+\left(\begin{array}{c} n \\ k_{1}, k_{2}-1, k_{3}, \ldots, k_{\ell} \end{array}\right)+\cdots+\left(\begin{array}{c} n \\ k_{1}, k_{2}, \ldots, k_{\ell}-1 \end{array}\right) \)