Toán Tính S= 1/5×9 + 1/9×13 + 1/13×17 +…..+ 1/41×45 17/07/2021 By Emery Tính S= 1/5×9 + 1/9×13 + 1/13×17 +…..+ 1/41×45
Đáp án: `S=2/45` Giải thích các bước giải: `S=1/(5xx9)+1/(9xx13)+1/(13xx17)+…+1/(41xx45)` `=1/4xx[1/5-1/9+1/9-1/13+1/13-1/17+…+1/41-1/45]` `=1/4xx[1/5-(1/9-1/9+1/13-1/13+1/17-…-1/41+1/45)]` `=1/4xx[1/5-1/45]` `=1/4xx8/45` `=2/45` vậy `S=2/45` Trả lời
S = 1/5×9 + 1/9×13 + 1/13×17 + … + 1/41×45 = 1/4 x (4/5×9 + 4/9×13 + 4/13×17 + … + 4/41×45) = 1/4 x (1/5 – 1/9 + 1/9 – 1/13 + 1/13 – 1/17 + … + 1/41 – 1/45) = 1/4 x (1/5 – 1/45) = 1/4 x (9/45 – 1/45) = 1/4 x 8/45 = 2/45 Trả lời
Đáp án:
`S=2/45`
Giải thích các bước giải:
`S=1/(5xx9)+1/(9xx13)+1/(13xx17)+…+1/(41xx45)`
`=1/4xx[1/5-1/9+1/9-1/13+1/13-1/17+…+1/41-1/45]`
`=1/4xx[1/5-(1/9-1/9+1/13-1/13+1/17-…-1/41+1/45)]`
`=1/4xx[1/5-1/45]`
`=1/4xx8/45`
`=2/45`
vậy `S=2/45`
S = 1/5×9 + 1/9×13 + 1/13×17 + … + 1/41×45
= 1/4 x (4/5×9 + 4/9×13 + 4/13×17 + … + 4/41×45)
= 1/4 x (1/5 – 1/9 + 1/9 – 1/13 + 1/13 – 1/17 + … + 1/41 – 1/45)
= 1/4 x (1/5 – 1/45) = 1/4 x (9/45 – 1/45)
= 1/4 x 8/45 = 2/45