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

Toán Lớp 7: tính tổng 1+ (-2) + (-2) mũ2 + -. + (-2) mũ 2006

Toán Lớp 7: tính tổng
1+ (-2) + (-2) mũ2 + ….. + (-2) mũ 2006

Comments ( 1 )

  1. Giải đáp:
    Đặt A=1+(-2)+(-2)^2+….+(-2)^2006
    <=>A=(-2)^0+(-2)^1+(-2)^2+….+(-2)^2006
    <=>-2A=(-2)^1+(-2)^2+(-2)^3+…..+(-2)^2007
    <=>-2A-A=(-2)^2007-(-2)^0
    <=>-3A=(-2)^2007-1
    <=>3A=2^2007+1
    <=>A=(2^2007+1)/3.

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

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