2/35+2/63+2/99+2/143+2/195+2/255 trả lời giúp em với ạ em đang cần gấp hứa sẽ vote 5 sao

$\dfrac{2}{35}$`+`$\dfrac{2}{63}$`+`$\dfrac{2}{99}$`+`$\dfrac{2}{143}$`+`$\frac{2}{195}$`+`$\dfrac{2}{255}$

`=2/5.7 + 2/7.9 + 2/9.11 + 2/11.13 + 2/13.15 + 2/15.17`

`= 1/5 – 1/7 + 1/7 – 1/9 + 1/9 – 1/11 + 1/11 – 1/13 + 1/13 – 1/15 + 1/15 – 1/17`

`= 1/5 – 1/17`

`= 17/85 – 5/85 = 12/85`