tìm D = 1/6x11+1/11x16+1/16x21+.....+1/ 2021x2026

Đáp án + Giải thích các bước giải:

`D = 1/(6xx11) + 1/(11xx16) + 1/(16xx21) + ... + 1/(2021 xx 2026)`

`5xxD = 5xx (1/(6xx11) + 1/(11xx16) + 1/(16xx21) + ... + 1/(2021 xx 2026))`

`5D = 5/(6xx11) + 5/(11xx16) + 5/(16xx21) + ... + 5/(2021 xx 2026)`

`5D =( 1/6 - 1/11) + (1/11 - 1/16 )+ (1/16 - 1/21) + .. + (1/2021 - 1/2026)`

`5D = 1/6 - 1/11 + 1/11 - 1/16 + 1/16 - 1/21 + .. + 1/2021 - 1/2026`

`5D = (1/6 - 1/2026) + (-1/11 + 1/11) + .. + (-1/2021 + 1/2021)`

`5D = 1/6 - 1/2026`

`5D = 1013/6078 - 3/6078`

`5D = 1010/6078`

`D = 1010/6078 . 1/5`

`D = 202/6078 = 101/3039`