d = 1 +1/2 * (1+2) +1/3 * (1+2+3) + … + 1/2020 * (1+2+3+ … +2020)

0 bình luận về “d = 1 +1/2 * (1+2) +1/3 * (1+2+3) + … + 1/2020 * (1+2+3+ … +2020)”

1. Ta có:

   ` D= 1+1/2 . (1+2)+1/3 . (1+2+3)+…+1/2020 . (1+2+3+…+2020) `

   ` <=> D= 1+ 1/2 . 3 +…+1/2020 . 2041210 `

   ` <=> D =1+1,5+2+…+ 1010,5 `

   ` <=> D = \frac{ (1010,5 + 1).[(1010,5 – 1) : 0,5 + 1] }{2} `

   ` <=> D = \frac{2043230}{2} `

   ` <=> D = 1021615 `

   Bình luận