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

Toán Lớp 7: Chứng minh `B=2^2+2^3+2^4+…+2^99+2^100` chia hết cho `7`

Toán Lớp 7: Chứng minh B=2^2+2^3+2^4+…+2^99+2^100 chia hết cho 7

Comments ( 2 )

  1. Giải đáp:
     
    Lời giải và giải thích chi tiết:
     Ta có: B=2^2+2^3+2^4+…+2^99+2^100
    ⇒B=(2^2+2^3+2^4)+…+(2^98+2^99+2^100)
    ⇒B=2^2(1+2+2^2)+…+2^98(1+2^2+2^2)
    ⇒B=2^2 .7+…+2^98 .7
    ⇒B=7(2^2+…+2^98)
    Vì 7\vdots7=>7(2^2+…+2^99)\vdots7 hay B\vdots7

  2. B=2^2+2^3+2^4+…+2^99+2^100
    B=(2^2+2^3+2^4)+(2^5+2^6+2^7)+…+(2^98+2^99+2^100)
    B=2^2(1+2+2^2)+2^5(1+2+2^2)+…+2^98(1+2+2^2)
    B=2^2 . 7+2^5 . 7+…+2^98 . 7
    B=7.(2^2+2^5+…+2^98)
    Vậy B\vdots7

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