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

Toán Lớp 7: Giúp mk thêm bài này nha Tính: B = `2^100` – `2^99` – `2^98` – … – `2^2` – `2`

Toán Lớp 7: Giúp mk thêm bài này nha
Tính:
B = 2^100 – 2^99 – 2^98 – … – 2^2 – 2

Comments ( 1 )

  1. B =2^100 – 2^99 – 2^98 –  … -2^2 -2
    => B = -(2 +2^2 + … +2^98 +2^99 + 2^100 )
    Đặt A =2 +2^2 + … +2^98 +2^99 + 2^100  -> B = -A
    =>2A = 2^2 +2^3 +…. +2^99 +2^100 +2^101
    => 2A – A = ( 2^2 +2^3 +…. +2^99 +2^100 +2^101) -(2 +2^2 + … +2^98 +2^99 + 2^100 )
    => A = 2^101 – 2
    => B = -A = -(2^201-2) = 2 -2^201
    Vậy B= 2 -2^201 .
     

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

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