nên \(\left|0.2x-3.1\right|+\left|0.2x+3.1\right|=0\)
<=> \(\left\{{}\begin{matrix}\left|0.2x-3.1\right|=0\\\left|0.2x+3.1\right|=0\end{matrix}\right.\) <=> \(\left\{{}\begin{matrix}0.2x-3.1=0\\0.2x+3.1=0\end{matrix}\right.\) <=> \(\left\{{}\begin{matrix}0.2x=3.1\\0.2x=-3.1\end{matrix}\right.\)<=>\(\left\{{}\begin{matrix}x=15.5\\x=-15.5\end{matrix}\right.\) (vô lý, vì 1 giá trị x ko thể có 2 giá trị)
Vậy ko có giá trị x nào thỏa mãn \(\left|0.2x-3.1\right|+\left|0.2x+3.1\right|=0\)
