i: Ta có: \(\left|x-3\right|=6\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=6\\x-3=-6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=9\\x=-3\end{matrix}\right.\)
k: Ta có: \(12-\left|x\right|=8\)
\(\Leftrightarrow\left|x\right|=4\)
hay \(x\in\left\{4;-4\right\}\)
