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

Toán Lớp 6: A=1-2+3-4+5-6+…+97-98+99- B=1+2+2 ²+2 ³+…+2^2019 help me

Toán Lớp 6: A=1-2+3-4+5-6+…+97-98+99-
B=1+2+2 ²+2 ³+…+2^2019
help me

Comments ( 2 )

  1. A=1-2+3-4+5-6+…+97-98+99-100
    A= ( 1-2) + (3-4) +(5-6)+…+(97-98)+(99-100)
    Ta có 100 : 2 = 50 cặp 
    => A = -1.50 = -50
    B=1+2+2 ²+2 ³+…+2^2019               (1)
    2B = 2+2²+2³+2^4 +…..+ 2^2020     (2)
    Lấy (2) (1) => B = 2^2020 –-1)

  2. A=1-2+3-4+5-6+…+97-98+99-100
    A= ( 1-2) + (3-4) +(5-6)+…+(97-98)+(99-100)
    Ta có 100 : 2 = 50 cặp 
    => A = -1.50 = -50
    B=1+2+2 ²+2 ³+…+2^2019               (1)
    2B = 2+2²+2³+2^4 +…..+ 2^2020     (2)
    Lấy (2) – (1) => B = 2^2020 – 1

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