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

Toán Lớp 6: Tìm tất cả các số nguyên n sao cho 3n + 1 chia hết cho n-2

Toán Lớp 6: Tìm tất cả các số nguyên n sao cho 3n + 1 chia hết cho n-2

Comments ( 2 )

  1. 3n+1 \vdots n-2

    => 3n-6+7 \vdotsn-2

    => 3(n-2)+7\vdots n-2 

    => 3(n-2) \vdots n-2 

    =>7 \vdots n-2

    => n-2 \in Ư(7)={-1,-7,1,7}

    => n={2,-5,3,9}

  2. 3n+1vdotsn-2
    =>3n-6+7vdotsn-2
    =>3(n-2)+7vdotsn-2
    =>3(n-2)vdots n-2
    =>7vdots n-2
    =>n-2in Ư(7)
    =>n-2 in{+-1;+-7}
    =>n in{3;1;9;-5}
    Vậy n in{3;1;9;-5}
    @Ki ng

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