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

Toán Lớp 7: thu gọn biểu thức S = 1 + 2 + 2^2 + 2^3 + .. + 2^50

Toán Lớp 7: thu gọn biểu thức S = 1 + 2 + 2^2 + 2^3 + .. + 2^50

Comments ( 2 )

  1. ~ Bạn tham khảo ~
    S = 1+2+2^2+2^3+….+2^50
    2S = 2+2^2 + 2^3+2^4+….+2^51
    2S – S = 2^51 – 1
    S = 2^51 -1
    Vậy S = 2^51 -1
    $#Vịt vàng$
     

  2. S = 1 + 2 + 2^ 2 + 2^3 + 2^ 4 + … + 2^ 49 + 2^ 50
    ⇒ 2 S = 2 ( 1 + 2 + 2^ 2 + 2 ^3 + 2^ 4 + … + 2 ^49 + 2^ 50 )
    2 S = 2 + 2 ^2 + 2^ 3 + 2^ 4 + 2^ 5 + … + 2^ 50 + 2 ^51
    ⇒2S−S=(2+2^2+2^3+2^4+2^5+…+2^50 + 1/2^51)−(1+2+2^2+2^3+2^4+…+2^49+2^50)
    S = 2 ^51 − 1
    Vậy S = 2^ 51 − 1
     

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