1/21+1/77+1/165+1/285+1/437+1/621 Giải giúp

0 bình luận về “1/21+1/77+1/165+1/285+1/437+1/621 Giải giúp”

1. `1/21+1/77+1/165+1/285+1/437+1/621`

   `=1/3.7+1/7.11+1/11.15+1/15.19+1/19.23+1/23.27`

   `=1/4(4/3.7+4/7.11+4/11.15+4/15.19+4/19.23+1/23.27)`

   `=1/4(1/3-1/7+1/7-1/11+1/11-1/15+1/15-1/19+1/19-1/23+1/23-1/27)`

   `=1/4(1/3-1/27)`

   `=1/4*8/27`

   `=2/27`

   Bình luận