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

Toán Lớp 7: CMR 2^0+2^1+2^2+…+2^5n-2+2^5n-1 chia hết cho 31 với n >0

Toán Lớp 7: CMR 2^0+2^1+2^2+…+2^5n-2+2^5n-1 chia hết cho 31 với n >0

Comments ( 1 )

  1. Ta có 2^0+2^1+2^2+…+2^(5n-2)+2^(5n-1)
    = 1 +2+2^2+…+2^(5n-2)+2^(5n-1)
    = (1+2+2^2+2^3+2^4)+…+2^(5n-1)+2^(5n-5)+2^(5n-4)+2^(5n-3)+2^(5n-2)
    = 31+ …+2^(5n-5).(1+2+2^2+2^3+2^4)
    =31+….+2^(5n-5).31$\vdots$ 31
    Vậy 2^0+2^1+2^2+…+2^(5n-2)+2^(5n-1)$\vdots$ 31

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

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