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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 6: M= 2+ 2^2 + 2^3 +… + 2^2024 Chứng tỏ M chia hết cho 30

Toán Lớp 6: M= 2+ 2^2 + 2^3 +… + 2^2024 Chứng tỏ M chia hết cho 30

Comments ( 2 )

  1. M = 2 + 2^2 + 2^3 + … + 2^2024
        = (2 + 2^2 + 2^3 + 2^4) + (2^5 + 2^6 + 2^7 + 2^8) + … + (2^2021 + 2^2022 + 2^2023 + 2^2024)
        = 30 + 2^4 . (2 + 2^2 + 2^3 + 2^4) + … + 2^2020 . (2 + 2^2 + 2^3 + 2^4)
        = 30 + 2^4 . 30 + … + 2^2020 . 30
        = 30 . (1 + 2^4 + … + 2^2020)
    –> M chia hết cho 30.

  2. M=2+2^2+2^3+2^4+…+2^2021+2^2022+2^2023+2^2021
    M=(2+2^2+2^3+2^4)+…+(2^2021+2^2022+2^2023+2^2021)
    M=1.(2+2^2+2^3+2^4)+…+2^2021(2+2^2+2^3+2^4)
    M=1.30+…+2^2021 .30
    M=(1+…+2^2021).30 \vdots 30
    =>M \vdots 30

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222-9+11+12:2*14+14 = ? ( )

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