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

Toán Lớp 7: Tìm x biết : $\frac{1}{7}$ <|x-$\frac{4}{7}$|< $\frac{3}{7}$

Toán Lớp 7: Tìm x biết :

$\frac{1}{7}$ <|x-$\frac{4}{7}$|< $\frac{3}{7}$

Comments ( 1 )

  1. Giải đáp:
    x∈{2; 3; 4; 5; 6}
    Lời giải và giải thích chi tiết:
    1/7<|x-4/7|<3/7
    ⇒$\left \{ {{\dfrac{1}{7}<x-\dfrac{4}{7}<\dfrac{3}{7}} \atop {\dfrac{1}{7}<\dfrac{4}{7}-x<\dfrac{3}{7}}} \right.$ 
    ⇒$\left \{ {{\dfrac{1}{7}<x<\dfrac{3}{7}+\dfrac{4}{7}} \atop {\dfrac{1}{7}<x<\dfrac{4}{7}-\dfrac{3}{7}}} \right.$ 
    ⇒$\left \{ {{\dfrac{1}{7}<x<\dfrac{7}{7}} \atop {\dfrac{1}{7}<x<\dfrac{1}{7}}} \right.$ ⇒$\left \{ {{1<x<7} \atop {1<x<1}} \right.$ ⇒$\left \{ {{x∈{2; 3; 4; 5; 6}} \atop {loại .do .vô .lý}} \right.$ 
    Vậy x∈{2; 3; 4; 5; 6}
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222-9+11+12:2*14+14 = ? ( )

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