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

Toán Lớp 6: A=1+3+3²+3³+–.. 3 mũ 100. A : hết cho 40

Toán Lớp 6: A=1+3+3²+3³+………. 3 mũ 100. A : hết cho 40

Comments ( 2 )

  1. A=1+3+3²+3³+3⁴+3⁵+3⁶+3⁷+…+3¹⁰⁰
    =>A=(1+3+3²+3³)+(3⁴+3⁵+3⁶+3⁷)+…+(3⁹⁷+3⁹⁸+3⁹⁹+3¹⁰⁰)
    =>A=40+3⁴(1+3+3²+3³)+…+3⁹⁷(1+3+3²+3³)
    =>A=40+3⁴.40+…+3⁹⁷.40
    =>A=40(1+3⁴+…+3⁹⁷)\vdots 40(đpcm)
    Vậy A\vdots 40

  2. Giải đáp:
    A=1+3+3^2+3^3+3^4+…+3^1979
    A=3^0+3^1+3^2+3^4+…+3^19799
    AS=30.(1+3+9+27)+…+3^1976.(1+3+9+27)
    ⇒A=3^0.40+…+3^1976.40
    ⇒A=(3^0+…+3^1976).40⋮40(đpcm)
    Cho mình 5*+cảm ơn+CTLHN nhé!
    @HaHieu
     

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