`Thiếu đề : 1/(2*3)`
`Sửa : 1/(2*3*4)`
`P = 1/(1*2*3) + 1/(2*3*4) + 1/(3*4*5) + ... + 1/(2017*2018*2019)`
`2P = 2/(1*2*3) + 2/(2*3*4) + 2/(3*4*5) + ... + 2/(2017*2018*2019)`
`2P = 1/(1*2) - 1/(2*3) + 1/(2*3) - 1/(3*4) + .... + 1/(2017*2018)-1/(2018*2019)`
`2P = 1/2 - 1/(2018*2019)`
`2P = 2037170/(2018*2019)`
`P = (2037170/(2018*2019))/2`
`P = 1018585/(2018*2019)`
`#KAITO#`
