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

Toán Lớp 6: Cho A = 2 + 2^2+ 2^3 +2^4+-…+2^60 . Chứng tỏ A chia hết cho 5.

Toán Lớp 6: Cho A = 2 + 2^2+ 2^3 +2^4+…….+2^60 . Chứng tỏ A chia hết cho 5.

Comments ( 2 )

  1. A = 2 + 2^2+ 2^3 +2^4+………………..+2^60
    A=(2+2^2+2^3+2^4)+……………….+(2^57+2^58++2^59+2^60)
    A=1.(2+2^2+2^3+2^4)+……………….+2^56.(2+2^2+2^3+2^4)
    A=1.30+……………….+2^56. 30
    A=30.(1+………………..+2^56)
    Vì 30vdots5
    =>Avdots5
     

  2. Lời giải và giải thích chi tiết:
    A = 2 + 2^2 + 2^3 + 2^4 + …….. + 2^60
    A = (2 + 2^2 + 2^3 + 2^4) + ………. + (2^57 + 2^58 + 2^59 + 2^60)
    A = 2(1 + 2 + 2^2 + 2^3) + ………….. + 2^57(1 + 2 + 2^2 + 2^3)
    A = 2 . 15 + ……….. + 2^57 . 15
    A = 15 . (2 + ……… + 2^57) \vdots 5
    => A \vdots 5

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

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