toán 11 gấp
1) cho
{0≤m≤k≤nk,m,n∈Zchứng minh
Ckn.C0m+Ck−1n.C1m+...+Ck−mn.Cmm=Ckn+m2)chứng minh $\frac{1}{C^{1}_{2017}}+\frac{1}{C^{2}_{2017}}+...+\frac{
201
7}{C^{2017}_{2017}}=\frac{1009}{2017}(\frac{1}{C^{0}_{2016}}+\frac{1}{C^{1}_{2016}}+...\frac{1}{C^{2016}_{2016}})$