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

Toán Lớp 6: tìm x biết : 3x + 7 chia hết cho 2x + 4

Toán Lớp 6: tìm x biết : 3x + 7 chia hết cho 2x + 4

Comments ( 1 )

  1. Giải đáp:
    x in {-14/3; -13/3; -11/3; -10/3}
    Lời giải và giải thích chi tiết:
    Vì 3x+7 vdots 2x+4
    =>2(3x+7) vdots 3(2x+4)
    =>6x+14 vdots 6x+12
    =>(6x+14)/(6x+12)=(6x+14+2)/(6x+12)=(6x+12)/(6x+12) + 2/(6x+12)=1 + 2/(6x+12)
    =>2 vdots 6x+12
    Mà 3(2x+4)=6x+12
    =>2 vdots 6x+12
    => 3x +4 in Ư(2)={-2;-1;1;2}
    Ta có bảng sau:
    \begin{array}{|c|c|c|}\hline \text{3x+12}&\text{-2}&\text{-1}&\text{1}&\text{2}\\\hline \text{3x}&\text{-14}&\text{-13}&\text{-11}&\text{-10}\\\hline \text{x}&\text{-14/3}&\text{-13/3}&\text{-11/3}&\text{-10/3}\\\hline\end{array}
    Vậy x in {-14/3; -13/3; -11/3; -10/3}

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