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

Toán Lớp 6: tính nhanh : A=1/2+1/2^2+1/2^3+-+1/2^10

Toán Lớp 6: tính nhanh : A=1/2+1/2^2+1/2^3+….+1/2^10

Comments ( 2 )

  1. #Quabotron
    Happy Christmas Day
    A=1/2+1/(2^2)+1/(2^3)+….+1/(2^10)
    2A=1+1/2+1/(2^2)+….+1/(2^9)
    2A – A = (1+1/2+1/(2^2)+….+1/(2^9)) – (1/2+1/(2^2)+1/(2^3)+….+1/(2^10))
    A = 1 – 1/(2^10)
    A = (2^10 – 1)/(2^10)

    toan-lop-6-tinh-nhanh-a-1-2-1-2-2-1-2-3-1-2-10

  2. Giải đáp:
     A=1023/1024
    Lời giải và giải thích chi tiết:
    A= 1/2 + 1/2^2+1/2^3+….+1/2^10
    =>2A= 1+1/2+1/2^2+…+1/2^9
    Lấy 2A-A= (1/2 + 1/2^2+1/2^3+….+1/2^10) – (1+1/2+1/2^2+…+1/2^9)
    A= 1-2^10
    A= 1-1/1024
    A= 1023/1024
     

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

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