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

Toán Lớp 6: cho S= 1+5^2+5^4+5^6+…+5^2020. Chứng minh rằng S chia hết cho 313

Toán Lớp 6: cho S= 1+5^2+5^4+5^6+…+5^2020. Chứng minh rằng S chia hết cho 313

Comments ( 2 )

  1. S = (1 + 5^2 + 5^4 + 5^6) +…+ (5^2014 + 5^2016 + 5^2018 + 5^2020)
    S = (1 + 5^2 + 5^4 + 5^6) +…+ 5^2014(1 + 5^2 + 5^4 + 5^6)
    S = (1 + 5^2 + 5^4 + 5^6)(1 +…+ 5^2014)
    S=16276(1 + 5^2 + 5^3 +…+  5^2014) ⋮ 313
    Mà 16276 ⋮ 313
    => S ⋮ 313
     

  2. S=(1+5^2+5^4+5^6)+….+(5^2014+5^2016+5^2018+5^2020)
    S=(1+5^2+5^4+5^6)+….+5^2014+(1+5^2+5^4+5^6)
    S=(1+5^2+5^4+5^6).(1+….+5^2014)
    S=16276.(1+5^2+5^4+….+5^2014)\vdots313
    Mà S=16276\vdots313
    ->S\vdots313
    #tcv

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