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

Toán Lớp 6: s=3+3¹+3²+3³+…+3⁶⁰ chia hết cho 13

Toán Lớp 6: s=3+3¹+3²+3³+…+3⁶⁰ chia hết cho 13

Comments ( 2 )

  1. Đề hơi sai sai vì có tới 2 số 3 mũ 1 nên mk sẽ sửa đề
    Sửa đề: S=3^1 +3^2 +3^3+3^4+3^5+3^6+…+3^58+3^59+3^60
    S=(3^1 +3^2 +3^3)+(3^4+3^5+3^6)+…+(3^58+3^59+3^60)
    S=1.(3^1 +3^2 +3^3)+3^3. (3^1+3^2+3^3)+…+3^57.(3^1+3^2+3^3)
    S=1.39+3^3 .39+…+3^57 .39
    S=39. (1+3^3+…+3^57)
    Vì 39 vdots 13=>39.(1+3^3+…+3^57) vdots 13=> S vdots 13 (đpcm)

  2. S=3+3^2+3^3+3^4+……………….+3^60
    S=(3+3^2+3^3)+(3^4+3^5+3^6)+…………..+(3^58+3^59+3^60)
    S=1.(3+3^2+3^3)+3^3.(3+3^2+3^3)+………..+3^57.(3+3^2+3^3)
    S=1.39+3^3. 39+…………+3^57. 39
    S=39.(1+3^3+………….+3^57)
    Vì 39vdots13
    =>Svdots13
     

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