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

Toán Lớp 6: Chứng minh rằng : 1, 2+2^2+2^3+–+2^10 chia hết cho 2, 3, 31 2, 1+3+3^2+3^3+–.+3^11 chia hết cho 4, 13 Giúp mik nha

Toán Lớp 6: Chứng minh rằng :
1, 2+2^2+2^3+……..+2^10 chia hết cho 2, 3, 31
2, 1+3+3^2+3^3+………+3^11 chia hết cho 4, 13
Giúp mik nha

Comments ( 1 )

  1. Giải đáp:
     1, 2 + 2^2 + 2^3 + ………… + 2^10
    = 2(1 + 2 + 2^2 + ………… + 2^9) \ vdots 2
    = (2 + 2^2) + (2^3 + 2^4) + ………… + (2^9 + 2^10)
    = 2(1 + 2) + 2^3(1 + 2) + ……….. + 2^9(1 + 2)
    = 3 . (2 + 2^3 + ………. + 2^9) \vdots 3
    = (2 + 2^2 + 2^3 + 2^4 + 2^5) + (2^6 + 2^7 + 2^8 + 2^9 + 2^10)
    = 2(1 + 2 + 4 + 8 + 16) + 2^6(1 + 2 + 4 + 8 + 16)
    = 31 . (2 + 2^6) \vdots 31
    2,
    1 +3 + 3^2 + 3^3 + ……….. + 3^11
    = (1 + 3) + (3^2 + 3^3) + ………. + (3^10 + 3^11)
    = 4 + 3^2(1 + 3) + …………… + 3^10(1 + 3)
    = 4(1 + 3^2 + ………. + 3^10) \vdots 4
    = (1 + 3 + 3^2) + (3^3 + 3^4 + 3^5) + ………… + (3^9 + 3^10 + 3^11)
    = 13 + 3^3(1 + 3 + 9)  + ………… + 3^9(1 + 3 + 9)
    = 13(1 + 3^3 + ……… + 3^9) \vdots 13
     

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

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