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

Toán Lớp 6: chứng tỏ rằng B= 1+3+3^2+3^3+3^4+…+3^2019 chia hết cho 20

Tháng Mười Hai 7, 2022 Toán học 2 Comments 0 views

Toán Lớp 6: chứng tỏ rằng B= 1+3+3^2+3^3+3^4+…+3^2019 chia hết cho 20

Comments ( 2 )

  1. bichhhathu
    bichhhathu
    7 Tháng Mười Hai, 2022 at 10:22 chiều
    Reply
    #LC
    B = 1+3+3^2+3^3+3^4+…+3^(2019)
    B=(1+3+3^2+3^3)+(3^4+3^5+3^6+3^7)+ …+(3^(2016)+3^(2017)+3^(2018)+3^(2019))
    B=(1+3+3^2+3^3)+3^4(1+3+3^2+3^3)+…+3^(2016)(1+3+3^2+3^3)
    B=40+40.3^4+…+40.3^(2016)
    B = 40(1+3^4+…+3^(2016))
    Vì 40\vdots20
    => B\vdots20

  2. tonhitruc
    tonhitruc
    7 Tháng Mười Hai, 2022 at 10:22 chiều
    Reply
    B=1+3+3^2+3^3+3^4+…….+3^2019
    B=(1+3+3^2+3^3)+(3^4+3^5+3^6+3^7)+……….+(3^2016+3^2017+3^2018+3^2019)
    B=1.(1+3+3^2+3^3)+3^4.(1+3+3^2+3^3)+………….+3^2016.(1+3+3^2+3^3)
    B=1.40+3^4. 40+…………..+3^2016. 40
    B=40.(1+3^4+……………..+3^2016)
    Vì 40vdots20
    =>Bvdots20 

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

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