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

Toán Lớp 6: Cho P=2-2^2+2^3-2^4+…+2^99-2^100.Rút gọn P

Toán Lớp 6: Cho P=2-2^2+2^3-2^4+…+2^99-2^100.Rút gọn P

Comments ( 2 )

  1. Giải đáp : P = \frac{2 – 2^101}{3}
    P = 2 – 2^2 + 2^3 – 2^4 + … + 2^99 – 2^100
    ⇒ 2P = 2^2 – 2^3 + 2^4 – 2^5 + … + 2^100 – 2^101
    ⇒ 2P + P = (2^2 – 2^3 + 2^4 – 2^5 + … + 2^100 – 2^101) + (2 – 2^2 + 2^3 – 2^4 + … +2^99 – 2^100)
    ⇒ 3P = (2^2 – 2^2) + (2^3 – 2^3) + …. + (2^100 – 2^100) + 2 – 2^101
    ⇒ 3P = 2 – 2^101
    ⇒ P = \frac{2 – 2^101}{3}

  2. P = 2 – 2^2 + 2^3 – 2^4 +……………………+ 2^99 – 2^100

    2P = 2^2 – 2^3 + 2^4 – 2^5 + ………………………. + 2^100 – 2^101

    2P + P = (2^2 – 2^3 + 2^4 – 2^5 +…………………… + 2^100 – 2^101) + (2 – 2^2 + 2^3 – 2^4 +………………. +2^99 – 2^100)

    3P = (2^2 – 2^2) + (2^3 – 2^3) +…………………………+ (2^100 – 2^100) + 2 – 2^101

    3P=2-2^101

    P=(2-2^101)/3

     

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