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

Toán Lớp 6: CMR : b) B=2+2^2+2^3+….+2^100 chia hết cho 31

Toán Lớp 6: CMR : b) B=2+2^2+2^3+….+2^100 chia hết cho 31

Comments ( 2 )

  1. a, B=2+2^2+2^3+…+2^100
    B= (2+2^2+2^3+2^4+2^5)+….+(2^96+2^97+2^98+2^99+2^100)
    B= 31.(2+2^6+2^11+…+2^96) chia hết cho 31
    ->B chia hết cho 31

  2. Giải đáp:
     
    Lời giải và giải thích chi tiết:
    B = 2 + 2^2 + 2^3 +…………+ 2^100
    B = ( 2 + 2^2 + 2^3 + 2^4 + 2^5 ) +…….+ ( 2^96 + 2^97 + 2^98 + 2^99 + 2^100 )
    B = 2 . ( 1 + 2 + 4 + 8 + 16 ) +…….+ 2^96 . ( 1 + 2 + 4 + 8 + 16 )
    B = 31 . ( 2 +…….+ 2^96 ) vdots 31
    -> B vdots 31
                    Vậy B vdots 31
    #haducdung2009 

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

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