\(\frac{4}{5}-\left|x+\frac{2}{5}\right|=-\frac{1}{10}\)
=> \(\left|x+\frac{2}{5}\right|=\frac{4}{5}-\left(-\frac{1}{10}\right)\)
=> \(\left|x+\frac{2}{5}\right|=\frac{9}{10}\)
=> \(\left\{{}\begin{matrix}x+\frac{2}{5}=\frac{9}{10}\\x+\frac{2}{5}=-\frac{9}{10}\end{matrix}\right.\) => \(\left\{{}\begin{matrix}x=\frac{9}{10}-\frac{2}{5}\\x=\left(-\frac{9}{10}\right)-\frac{2}{5}\end{matrix}\right.\)
=> \(\left\{{}\begin{matrix}x=\frac{1}{2}\\x=-\frac{13}{10}\end{matrix}\right.\)
Vậy x \(\in\) \(\left\{\frac{1}{2};-\frac{13}{10}\right\}\).
Chúc bạn học tốt!