Đáp án:
`x∈{2; 3; 4; 5; 6}`
Giải thích các bước giải:
`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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