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

Toán Lớp 8: Biết `(4x)/(2-x)∈Z`, tìm `x∈Z`

Toán Lớp 8: Biết (4x)/(2-x)∈Z, tìm x∈Z

Comments ( 1 )

  1. ĐK: xne 2
    Ta có : (4x)/(x-2)=-4+8/(2-x)
    Để (4x)/(2-x) in ZZ thì :
    -4+8/(2-x) in ZZ 
    =>8 vdots 2-x hay 2-x là Ư(8)
    Mà Ư(8)={pm1;pm2;pm4;pm8}
    + 2-x=1<=>x=1(tm)
    + 2-x=-1<=>x=3(tm)
    + 2-x=2<=>x=0(tm)
    + 2-x=-2<=>x=4(tm)
    + 2-x=4<=>x=-2(tm)
    + 2-x=-4<=>x=6(tm)
    + 2-x=8<=>x=-6(tm)
    + 2-x=-8<=>x=10(tm)
    Vậy x in {-6;-2;0;1;3;4;6;10} thì (4x)/(2-x) in ZZ 

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