A= 2018+2017/2+2016/3+….+1/2018 ————————————————— 1/2+1/3+1/4+….+1/

0 bình luận về “A= 2018+2017/2+2016/3+….+1/2018 ————————————————— 1/2+1/3+1/4+….+1/”

1. Ta có: `2018+2017/2+2016/3+…+1/2018`

   `= (2018+1) + (2017/2+1 )+ (2016/3+1) +…+(1/2018+1) -2018` ( vì có 2018 số hạng )

   `= 2019 + (2017/2+2/2 )+ (2016/3+3/3) +…+(1/2018+2018/2018) -2018 `

   `= (2019 – 2018 ) + 2019/2 + 2019/3 +…+2019/2018 `

   `= 1 + 2019/2 + 2019/3 +…+2019/2018 `

   `=  2019/2 + 2019/3 +…+2019/2018 + 2019/2019 `

   `=  2019× (1/2 + 1/3 +…+1/2018 + 1/2019) `

   Thay `2018+2017/2+2016/3+…+1/2018“=2019× (1/2 + 1/3 +…+1/2018 + 1/2019)` vào `A` ta có:

   `A=\frac{2019× (1/2 + 1/3 +…+1/2018 + 1/2019)}{1/2+1/3+1/4+….+1/2019}`

   `A=2019.1/1`
   `A=2019.`
   Vậy `A=2019.`

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