[tex]\it |a| =b \Longleftrightarrow a = \pm b,\ \ \ \forall b\geq0
[/tex]
[tex]\it |x| = 18 \Leftrightarrow x = \pm18 \Leftrightarrow \begin{cases}\it x_1 = -18
\\
\it x_2 \ =\ 18\end{cases}[/tex]
[tex]\it |x-3| = 0 \Leftrightarrow x-3 = 0 \Leftrightarrow x = 3[/tex]
[tex]\it |x-5| = 1 \Leftrightarrow x-5 = \pm1 \Leftrightarrow \begin{cases} \it x-5=-1 \Leftrightarrow x=4
\\ \it x-5\ = \ 1 \Leftrightarrow x = 6 \end{cases}[/tex]
