Question

[hộ toán khó]

giá tri x > 0 nguyên thoa mãn ( nghĩ quá hại não mất = ) :

-7/3 < | 2/7 -x | -5/2 < -7/4

hộ mình làm cái gải da nha:

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Answer 1

[Nguyễn Lê Phước Thịnh]

\(\Leftrightarrow\dfrac{1}{6}< \left|x-\dfrac{2}{7}\right|< \dfrac{3}{4}\)

\(\Leftrightarrow\left\{{}\begin{matrix}\left|x-\dfrac{2}{7}\right|< \dfrac{3}{4}\\\left|x-\dfrac{2}{7}\right|>\dfrac{1}{6}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}-\dfrac{13}{28}< x< \dfrac{29}{28}\\\left[{}\begin{matrix}x>\dfrac{19}{42}\\x< \dfrac{5}{42}\end{matrix}\right.\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}-\dfrac{13}{28}< x< \dfrac{5}{42}\\\dfrac{19}{42}< x< \dfrac{29}{28}\end{matrix}\right.\)