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

Toán Lớp 6: cho b = 3^1 + 3^2 + 3^3+…+3^100 chứng minh b chia hết cho 3

Toán Lớp 6: cho b = 3^1 + 3^2 + 3^3+…+3^100 chứng minh b chia hết cho 3

Comments ( 2 )

  1. B = 3^1 + 3^2 + 3^3 + …. + 3^100
    3B = 3^2 + 3^3 + 3^4 + …… + 3^100 + 3^101
    3B – B = (3^2 + 3^3 + 3^4 + …. + 3^101) – (3 + 3^2 + ….. + 3^100)
    2B = 3^101 – 3
    B = frac{3^101 – 3}{2} \vdots 2
     

  2. B=3^1 + 3^2 +3^3 +3^4 +…+3^100
    =>B=3(1+3+3^2 + 3^3 + … + 3^99 )\vdots 3(đpcm)
    Vậy B\vdots 3

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

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