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

Toán Lớp 7: CTR:A=`3^{5n+2}`+`3^{5n+1}`-`3^{5n}` chia hết cho 11

Toán Lớp 7: CTR:A=3^{5n+2}+3^{5n+1}-3^{5n} chia hết cho 11

Comments ( 2 )

  1. 3^(5x+2)+3^(5x+1)-3^(5n)
    =3^(5n)(3^2+3-1)
    =3^(5n)(9+2)
    =3^(5n). 11 chia hết cho 11 (ĐPCM)
    $_Ativity_$

  2. A=3^{5n+2}+3^{5n+1}+3^{5n}
    A=3^{5n}·3²+3^{5n}·$3^1$-3^{5n}·1
    A=3^{5n}·(3²+$3^1$+1) 
    A=3^{5n}·11 mà 11$\vdots$11
    ⇒A$\vdots$11
     

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

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