Giải thích các bước giải:
\(\begin{array}{l}
B2:\\
a.\left\{ \begin{array}{l}
x \ge 7\\
2x > 12
\end{array} \right. \to \left\{ \begin{array}{l}
x \ge 7\\
x > 6
\end{array} \right.\\
\to x \ge 7\\
b.\left\{ \begin{array}{l}
x > - \frac{{16}}{7}\\
\frac{1}{2}x > \frac{{13}}{2}
\end{array} \right. \to \left\{ \begin{array}{l}
x > - \frac{{16}}{7}\\
x > 13
\end{array} \right.\\
\to x > 13\\
c.\left\{ \begin{array}{l}
3x \le - 2\\
3x < 15
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x \le - \frac{2}{3}\\
x < 5
\end{array} \right.\\
\to x \le - \frac{2}{3}\\
B3:\\
a.DK:x \ne \left\{ { - 1;2} \right\}\\
b.DK:\left\{ \begin{array}{l}
{x^2} - 4 \ne 0\\
{x^2} - 3x + 2 \ne 0
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x \ne \pm 2\\
x \ne 1
\end{array} \right.\\
c.DK:x \ge 3
\end{array}\)
