Question

giup voi

Answer 1

`4/(10xx12)+  4/(12xx14) + ... + 4/(186xx188)`

`= 2. (1/10 - 1/12 + 1/2 - 1/14+ ...+1/186 - 1/188)`

`=2 . (1/10 - 1/188)`

`= 2. 89/940`

`=89/470`

Answer 2

\(=2\left(\dfrac{2}{10\times12}+\dfrac{2}{12\times14}+...+\dfrac{2}{186\times188}\right)\\ =2\left(\dfrac{1}{10}-\dfrac{1}{12}+\dfrac{1}{12}-\dfrac{1}{14}+...+\dfrac{1}{186}-\dfrac{1}{188}\right)\\ =2\left(\dfrac{1}{10}-\dfrac{1}{188}\right)=2\times\dfrac{89}{940}=\dfrac{89}{470}\)

Answer 3

\(\dfrac{89}{470}\)