Tìm x, biết: |x| =1/4 +4/7

* Hướng dẫn giải

$\begin{array}{l}a)x\in \left\{\pm \frac{23}{28}\right\}.\\ \\ b)x\in \left\{\frac{-23}{6};\frac{35}{6}\right\}.\\ \\ c)x\in \left\{\frac{-17}{60};\frac{97}{60}\right\}.\\ \\ d)x\in \left\{\frac{67}{140};\frac{143}{140}\right\}.\end{array}$