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

Toán Lớp 6: S = 1+2+ 2^2 + 2^3+ 2^4 + 2^5 + 2^6 +…+ 2^99 so sanh voi 5 . 2^98

Toán Lớp 6: S = 1+2+ 2^2 + 2^3+ 2^4 + 2^5 + 2^6 +…+ 2^99 so sanh voi 5 . 2^98

Comments ( 2 )

  1. Giải đáp:
     
    Lời giải và giải thích chi tiết:
    S = 1 + 2 +……….+ 2^99
    => 2S = 2 + 2^2 +……….+ 2^100
    => 2S – S = 2^100 – 1 
    => S = 2^98 . 4 – 1 < 2^98 . 5
    =. S < 2^98 . 5

  2. S = 1+2+ 2^2 + 2^3+ 2^4 + 2^5 + 2^6 +…+ 2^99
    2.S= 2+ 2^2 + 2^3+ 2^4 + 2^5 + 2^6 +…+ 2^100
    2S-S= (2+ 2^2 + 2^3+ 2^4 + 2^5 + 2^6 +…+ 2^100)- (1+2+ 2^2 + 2^3+ 2^4 + 2^5 + 2^6 +…+ 2^99)
    S= 2^100 – 1
    S = 2^98 . 2^2 -1
    Vì 2^2=4 < 5 ⇒ 2^98 . 2^2 -1 < 2^98 . 5 hay A<5 . 2^98
    Vậy A<5. 2^98
     

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