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

Toán Lớp 6: M=2+2²+2³+2⁴+…+2²⁰+2²¹ Chứng tỏ M chia hết cho 7

Toán Lớp 6: M=2+2²+2³+2⁴+…+2²⁰+2²¹
Chứng tỏ M chia hết cho 7

Comments ( 2 )

  1. M = 2 + 2^2 + 2^3 + 2^4 + … + 2^20 + 2^21
    => M = ( 2 + 2^2 + 2^3 ) + ( 2^4 + 2^5 + 2^6 ) + … + ( 2^19 + 2^20 + 2^21 )
    => M = 2 . ( 1 + 2 + 2^2 ) + 2^4 . ( 1 + 2 + 2^2 ) + … + 2^19 . ( 1 + 2 + 2^2 )
    => M = 2 . 7 + 2^4 . 7 + … + 2^19 . 7
    => M = 7 . ( 2 + 2^4 + … + 2^19 ) \vdots 7
    Vậy M \vdots 7
    #dtkc
     

  2. Giải đáp+Lời giải và giải thích chi tiết:
    M=2+2^2 + 2^3 + 2^4 +…+2^20 + 2^21
    M= (2+ 2^2 + 2^3)+…+(2^19+2^20+2^21)
    M= (2+ 2^2 + 2^3)+…+2^18 . (2+2^2+2^3)
    M= 14+…+2^18 . 14
    M=14 . (1+…+2^18) $\vdots$ 7
    Vậy M $\vdots$ 7.

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