toán 11 gấp
$1)$ cho $\begin{cases}0\leq m\leq k\leq n\\ k, m, n \in Z\end{cases}$chứng minh $C^{k}_{n}.C^{0}_{m}+C^{k-1}_{n}.C^{1}_{m}+...+C^{k-m}_{n}.C^{m}_{m}=C^{k}_{n+m}$$2)$chứng minh $\frac{1}{C^{1}_{2017}}+\frac{1}{C^{2}_{2017}}+...+\frac{1}{C^{2017}_{2017}}=\frac{1009}{2017}(\frac{1}{C^{0}_{2016}}+\frac{1}{C^{1}_{2016}}+...\frac{1}{C^{2016}_{2016}})$
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toán 11 gấp
$1)$ cho $\begin{cases}0\leq m\leq k\leq n\\ k, m, n \in Z\end{cases}$chứng minh $C^{k}_{n}.C^{0}_{m}+C^{k-1}_{n}.C^{1}_{m}+...+C^{k-m}_{n}.C^{m}_{m}=C^{k}_{n+m}$$2)$chứng minh $\frac{1}{C^{1}_{2017}}+\frac{1}{C^{2}_{2017}}+...+\frac{
201
7}{C^{2017}_{2017}}=\frac{1009}{2017}(\frac{1}{C^{0}_{2016}}+\frac{1}{C^{1}_{2016}}+...\frac{1}{C^{2016}_{2016}})$
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toán 11 gấp
$1)$ cho $\begin{cases}0\leq m\leq k\leq n\\ k, m, n \in Z\end{cases}$chứng minh $C^{k}_{n}.C^{0}_{m}+C^{k-1}_{n}.C^{1}_{m}+...+C^{k-m}_{n}.C^{m}_{m}=C^{k}_{n+m}$$2)$chứng minh $\frac{1}{C^{1}_{2017}}+\frac{1}{C^{2}_{2017}}+...+\frac{1}{C^{2017}_{2017}}=\frac{1009}{2017}(\frac{1}{C^{0}_{2016}}+\frac{1}{C^{1}_{2016}}+...\frac{1}{C^{2016}_{2016}})$
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