a. $|x-3|=5$
⇒ \(\left[ \begin{array}{l}x-3=5\\x-3=-5\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=5+3\\x=-5+3\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=8\\x=-2\end{array} \right.\)
Vậy $x=-2$ hoặc $x=8$
b. $|2x-4|=-24-43 $
⇒ $|2x-4|=-67 $ ( vô lí do $|2x-4|≥0$)
Vậy $x∈∅$