1) l 2x +3 l - x + 5 = 0
| 2x +3 | - x = -5
| 2x - 3 | = -5 - x
⇒ \(\left[ \begin{array}{l}2x-3=-5-x\\2x-3=-(-5-x)\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}2x-x=-8\\2x-x=2\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=-8\\x=2\end{array} \right.\)
Vậy x ∈ { -8 ; 2 }
2) l -x + 4 l - 2x + 1 = 0
| -x + 4 | - 2x = -1
| -x + 4 | = -1 + 2x
⇒ \(\left[ \begin{array}{l}-x+4=-1+2x\\-x+4=-(-1+2x)\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}-x-2x=-1-4\\-x-2x=1-4\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}-3x=-5\\-3x=-3\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=\frac{5}{3} \\x=-1\end{array} \right.\)
Vậy x ∈ { `5/3` ; -1 }
