

m.n chỉ bài này mình với ạ
[tex]S_{1}=C_{n}^{0}+\frac{1}{2}.C_{n}^{1}+\frac{1}{3}.C_{n}^{2}+.....+\frac{1}{n+1}.C_{n}^{n}[/tex]
[tex]S_{2}=5.C_{0}^{n}+\frac{6^{2}-1}{2}.C_{n}^{1} +\frac{6^{3}-1}{3}.C_{n}^{2}+....+\frac{6^{n+1}-1}{n+1}.C_{n}^{n}[/tex]
[tex]S_{1}=C_{n}^{0}+\frac{1}{2}.C_{n}^{1}+\frac{1}{3}.C_{n}^{2}+.....+\frac{1}{n+1}.C_{n}^{n}[/tex]
[tex]S_{2}=5.C_{0}^{n}+\frac{6^{2}-1}{2}.C_{n}^{1} +\frac{6^{3}-1}{3}.C_{n}^{2}+....+\frac{6^{n+1}-1}{n+1}.C_{n}^{n}[/tex]