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

Toán Lớp 7: 1/2+2/2^2+3/2^3+…+100/2^100 <2

Tháng Mười 2, 2022 Toán học 1 Comment 0 views

Toán Lớp 7: 1/2+2/2^2+3/2^3+…+100/2^100 <2

Comments ( 1 )

  1. hoaiphuong85
    hoaiphuong85
    2 Tháng Mười, 2022 at 9:31 chiều
    Reply
    Cho A = 1/2+2/2^2+3/2^3+…+100/2^100
    A = 1/2+2/2^2+3/2^3+…+100/2^100
    2A = 1+1+3/2^2+…+100/2^99
    2A-A = (1+1+3/2^2+…+100/2^99)-(1/2+2/2^2+3/2^3+…+100/2^100)
    A = 1+ 1/2 + 1/2^2+ …+ 1/2^99 – 100/2^100
    Cho B = 1+ 1/2 + 1/2^2+ …+ 1/2^99
    2B = 2+1 + 1/2^2 + …+1/2^98
    2B-B = (2+1 + 1/2^2 + …+1/2^98)-(1+ 1/2 + 1/2^2+ …+ 1/2^99)
    B = 2 – 1/2^99
    Vậy A = 2 – 1/2^99 – 100/2^100 < 2
     

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

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