Tính: 1+2+2^2+…+2^2021/20^2023-2

Question

Tính: 1+2+2^2+…+2^2021/20^2023-2

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Mít Mít 5 years 2021-04-27T22:22:43+00:00 2 Answers 164 views 0

Answers ( )

  1. ngocdiep
    0
    2021-04-27T22:24:06+00:00
    Reply

    Đáp án + Giải thích các bước giải:

    Sửa : `20^2023 \to 2^2023`

    `TS=1+2+2^2+…+2^2021`

    `2TS=2+2^2+2^3+…+2^2022`

    `2TS-TS=2^2022-1`

    `TS=2^2022-1`

    $\\$

    `to \ \ (2^2022-1)/(2^2023-2)=(2^2022-1)/(2.(2^2022-1))=1/2`

  2. thienthi
    0
    2021-04-27T22:24:33+00:00
    Reply

    Đặt `A= 1+2+2^2 +…+2^2021`

    `2A = 2(1+2+2^2+…+22021)`

    `2A= 2 +2^2 +2^3+…+2^2022`

    `2A-A = 2+2^2 +2^3+…+2^2022 – 1 -2 -2^2-…-2^2021`

    `A= 2^2022-1`

    `=>(1+2+2^2+…+2^2021)/(20^2023-2)`

    `= (2^2022-1)/(20^2023-2)`

     

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Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )