|5x-4|=4-5x

* Hướng dẫn giải

$\begin{array}{l}\left|5x-4\right|=4-5x\left(8\right)\\ +)x\ge \frac{4}{5}\Rightarrow \left(8\right)\iff 5x-4=4-5x\iff x=\frac{4}{5}(tm)\\ +)x<\frac{4}{5}\Rightarrow \left(8\right)\iff 4-5x=4-5x\iff x\in ℝ/x<\frac{4}{5}S=\left\{x/x\le \frac{4}{5}\right\}\end{array}$