vì /-x/ luôn luôn lớn hơn hoặc bằng 0 nên
/-x/<5 <=> \(\left[\begin{matrix}\left|-x\right|=4\\\left|-x\right|=3\\\left|-x\right|=2\\\left|-x\right|=1\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}\left[\begin{matrix}-x=4\\-x=-4\end{matrix}\right.\\\left[\begin{matrix}-x=3\\-x=-3\end{matrix}\right.\\\left[\begin{matrix}-x=2\\-x=-2\end{matrix}\right.\\\left[\begin{matrix}-x=1\\-x=-1\end{matrix}\right.\end{matrix}\right.\)\(\Leftrightarrow\left[\begin{matrix}\left[\begin{matrix}x=-4\\x=4\end{matrix}\right.\\\left[\begin{matrix}x=-3\\x=3\end{matrix}\right.\\\left[\begin{matrix}x=-2\\x=2\end{matrix}\right.\\\left[\begin{matrix}x=-1\\x=1\end{matrix}\right.\end{matrix}\right.\)
/-x/=5<=>[-x=0<=>x=0 ( chỗ này mik đánh thiếu nên thêm vô nha bn)
Vậy x\(\in\left\{0;-1;1;-2;2;-3;3;-4;4\right\}\)
