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

Toán Lớp 6: A=1+2+2^2 … 2^2019 . Chứng minh A chia hết cho 7.

Toán Lớp 6: A=1+2+2^2 … 2^2019 . Chứng minh A chia hết cho 7.

Comments ( 2 )

  1. $\text{ A = 1 + 2 + $2^2$ + … + $2^{2019}$ }$
    $\text{ A = ( 1 + 2 + $2^2$ ) + … + ( $2^{2017}$ + $2^{2018}$ + $2^{2019}$ ) }$
    $\text{ A = ( 1 + 2 + $2^2$ ) + … + $2^{2017}$. ( 1 + 2 + $2^2$ ) }$
    $\text{ A = 7 + … + $2^{2017}$. 7 }$
    $\text{ A = 7. ( 1 + … + $2^{2017}$ )    $\vdots$ 7   ( đpcm ) }$

  2. Lời giải chi tiết:
    A=1+2+2^2+…+2^2019
    A=(1+2+2^2)+…+(2^2017+2^2018+2^2019)
    A=1.(1+2+2^2)+…+2^2017.(1+2+2^2)
    A=1.7+…+2^2017.7
    A=7.(1+…+2^2017)\vdots7
    Vậy A\vdots7
    @uniquetimehunter

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