Question

[Ngô Đặng Thùy Trúc]

CMR : 1/2!+2/3!+3/4! + ...+2013/2014! < 1

Answer 1

[Michiel Girl mít ướt]

ủa, nó nhỏ hơn 1 mà sao bn lại ghi lớn hơn 1

Answer 2

[Đinh Tuấn Việt]

\(\frac{1}{1.2}+\frac{2}{1.2.3}+\frac{3}{1.2.3.4}+...+\frac{2013}{1.2...2014}\)

\(=\frac{1}{2}+\frac{1}{1.3}+\frac{1}{1.2.4}+...+\frac{1}{1.2...2012.2014}\)

\(=\frac{1.1.3.4...2012.2014}{2.1.3.4...2012.2014}+\frac{1.2.4.5...2012.2014}{1.3.2.4.5...2012.2014}+...+\frac{1}{1.2.....2012.2014}\)(Quy đồng mẫu)

\(=\frac{1.1.3.4...2012.2014+1.2.4.5...2012.2014+...+1}{1.2...2012.2014}>1\)