Question

Tính: 4/1.5+4/5.9+...+4/2001.2005

 

Answer 1

\(=\frac{2014}{2015}\)

tk mk nha

Answer 2

Ta có : 

4/1 . 5 + 4/5 . 9 + ...+ 4/2001 . 2005 

= 1 - 1/5 + 1/5 - 1/9 + ...+ 1/2001 - 1/2005 

= 1 - 1/2005

=  2004/2005 

Tham khảo nha !!! 

Answer 3

lộn

\(=\frac{2004}{2005}\)

xl nha

Answer 4

Đặt A=\(\frac{4}{1\cdot5}+\frac{4}{5\cdot9}+...+\frac{4}{2001\cdot2005}\)

\(\Rightarrow A=1-\frac{1}{5}+\frac{1}{5}-\frac{1}{9}+...+\frac{1}{2001}-\frac{1}{2005}\)

\(\Rightarrow A=1-\frac{1}{2005}\)

\(\Rightarrow A=\frac{2004}{2005}\)

Answer 5

Ta có 

\(\frac{4}{1\cdot5}+\frac{4}{5\cdot9}+...+\frac{4}{2001\cdot2005}\)

\(=1-\frac{1}{5}+\frac{1}{5}-\frac{1}{9}+...+\frac{1}{2001}-\frac{1}{2005}\)

\(=1-\frac{1}{2005}\)

\(=\frac{2004}{2005}\)

Answer 6

Đặt \(A=\frac{4}{1.5}+\frac{4}{5.9}+\frac{4}{9.13}+...+\frac{1}{2001.1005}\)

\(\Rightarrow A=1-\frac{1}{5}+\frac{1}{5}-\frac{1}{9}+\frac{1}{9}-\frac{1}{13}+...+\frac{1}{2001}-\frac{1}{2005}\)

\(\Rightarrow A=1-\frac{1}{2005}\)

\(\Rightarrow A=\frac{2004}{2005}\)