~ Bạn tham khảo ~
` 2 : x = 1/2 + 1/6 + 1/12 + 1/20 + .... + 1/132`
`2 : x = 1/(1.2)+ 1/(2.3) + 1/(3.4)+1/(4.5) + .... + 1/(11.12)`
`2 : x = 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + ..... + 1/11 - 1/12`
`2 : x = 1 - 1/12`
`2 : x = 11/12`
`x = 2 : 11/12`
`x = 2 . 12/11`
`x = 24/11`
Vậy ` x = 24/11`