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

Toán Lớp 6: A = 3 +3^2 +3^3 +3^4 +3^5+3^6- +3^99+ 3^100 chứng tỏ a:12

Toán Lớp 6: A = 3 +3^2 +3^3 +3^4 +3^5+3^6…. +3^99+ 3^100
chứng tỏ a:12

Comments ( 2 )

  1. Ta có:
    A = 3+3^2+3^3+…+3^99+3^100
    = (3+3^2) + (3^3+3^4) +…+ (3^99 + 3^100)
    = 1. (3+3^2) + 3^3.(3+3^2) +…+ 3^99.(3+3^2)
    = 1. 12 + 3^3. 12 +…+ 3^99. 12
    = 12.(1 + 3^3 +…+ 3^99) vdots 12
    => A vdots 12 (đpcm)
     

  2. Lời giải chi tiết:
    A=3+3^2+3^3+…+3^99+3^100
    A=(3+3^2)+(3^3+3^4)+…+(3^99+3^100)
    A=1.(3+3^2)+3^2.(3+3^2)+…+3^98.(3+3^2)
    A=3^(0).12+3^(2).12+…+3^(98).12
    A=12.(3^0+3^2+…+3^98)
    =>A\vdots12 (đpcm)
    @uniquetimehunter

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

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