Question

Tính A= 1 phần 1.3+1 phần 3.5 + 1 phần 5.7+.......+1 phần 2017.2019  

 

Answer 1

A=1/1*3+1/3*5+...+1/2017*2019

2A=2/1*3+2/3*5+...+2/2017*2019

2A=1-1/3+1/3-1/5+..+1/2017-1/2019

2A=1-1/2019

2A=2018/2019

A=(2018/2019):2

A=1009/2019

Answer 2

A=1009/2019

Answer 3

\(A=\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{2017.2019}\)

\(A=\frac{1}{2}.\left(\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{2017.2019}\right)\)

\(A=\frac{1}{2}.\left(\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{2017}-\frac{1}{2019}\right)\)

\(A=\frac{1}{2}.\left(1-\frac{1}{2019}\right)\)

\(A=\frac{1}{2}.\frac{2018}{2019}\)

\(A=\frac{1009}{2019}\)

Answer 4

2A=2/1.3+2/3.5+2/5.7+.........+2/2017.2019

=>2A=1/1-1/3+1/3-1/5+1/5-1/7+..........+1/2017-1/2019

=>2A=1/1-1/2019

=>2A=2018/2019

=>A=2018/4038=1009/2019

Vậy A = 1009/2019

Answer 5

\(A=\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{2017.2019}\)

\(\Rightarrow2A=\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{2017.2019}\)

\(\Rightarrow2A=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2017}-\frac{1}{2019}\)

\(\Rightarrow2A=1-\frac{1}{2019}\)

\(\Rightarrow2A=\frac{2018}{2019}\)

\(\Rightarrow A=\frac{2018}{2019}\div2\)

\(\Rightarrow A=\frac{2018}{2019}\times\frac{1}{2}\)

\(\Rightarrow A=\frac{1009}{2019}\)

Answer 6

\(A=\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{2017.2019}\)

\(\Rightarrow A=\frac{1}{2}\left(\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{2017.2019}\right)\)

\(\Rightarrow A=\frac{1}{2}\left(\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{2017}-\frac{1}{2019}\right)\)

\(\Rightarrow A=\frac{1}{2}\left(1-\frac{1}{2019}\right)\)

\(\Rightarrow A=\frac{1}{2}.\frac{2018}{2019}\)

\(\Rightarrow A=\frac{1009}{2019}\)

Answer 7

\(A=\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{2017.2019}\)

   \(=1-\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2017}-\frac{1}{2019}\)

   \(=1-\frac{1}{2019}\)

   \(=\frac{2018}{2019}\)

Study well ! >_<

Answer 8

\(A=\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{2017.2019}\)

   \(=\frac{1}{2}\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{2017.2019}\right)\)

   \(=\frac{1}{2}\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2017}-\frac{1}{2019}\right)\)

   \(=\frac{1}{2}\left(1-\frac{1}{2019}\right)\)

   \(=\frac{1}{2}.\frac{2018}{2019}\)

   \(=\frac{1009}{2019}\)

Study well ! >_<