Question

[Đinh Thị Ngọc Anh]

Câu1:Chứng minh:

\(1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{2k-1}-\frac{1}{2k}=\frac{1}{k+1}+\frac{1}{k+2}+...+\frac{1}{2k}\)

Câu 2:Cho \(S_n=1+\frac{1}{2}+\frac{1}{3}+...+\frac{1}{n}\).Chứng minh :

a)\(S_n=n-\left(\frac{1}{2}+\frac{2}{3}+\frac{3}{4}+...+\frac{n-1}{n}\right)\)

b)n\(S_n=n+\frac{n-1}{1}+\frac{n-2}{2}+...+\frac{2}{n-2}+\frac{1}{n-1}\)

Answer 1

[Nguyễn Thu Phương]

ai tick cho mk mk tick lai cho