Giải thích các bước giải:
\(\begin{array}{l}
a.\left[ \begin{array}{l}
x - 6 = 6 - x\\
x - 6 = - 6 + x
\end{array} \right.\\
\to \left[ \begin{array}{l}
2x = 12\\
0 = 0\left( {ld} \right)
\end{array} \right.\\
\to x = 6\\
b.\left| {x - 2} \right| \le 1\\
\to \left[ \begin{array}{l}
x - 2 \le 1\\
x - 2 \ge - 1
\end{array} \right.\\
\to \left[ \begin{array}{l}
x \le 3\\
x \ge 1
\end{array} \right.\\
c.0 < \left| {x + 1} \right| \le 3\\
\to \left[ \begin{array}{l}
\left\{ \begin{array}{l}
0 < x + 1\\
x + 1 \le 3
\end{array} \right.\\
\left\{ \begin{array}{l}
0 > x + 1\\
x + 1 \ge - 3
\end{array} \right.
\end{array} \right.\\
\to \left[ \begin{array}{l}
\left\{ \begin{array}{l}
x > - 1\\
x \le 2
\end{array} \right.\\
\left\{ \begin{array}{l}
x < - 1\\
x \ge - 4
\end{array} \right.
\end{array} \right.
\end{array}\)
