Đáp án:
\(\begin{array}{l}
a)x \le - 4\\
c)5 > x > 4\\
b)x \ge 1\\
d)\left[ \begin{array}{l}
x \le - 4\\
x \ge 5
\end{array} \right.
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a)2x + 8 \le 0\\
\to x \le - 4\\
c)\left( {2x - 8} \right)\left( {15 - 3x} \right) > 0\\
\to \left[ \begin{array}{l}
\left\{ \begin{array}{l}
2x - 8 > 0\\
15 - 3x > 0
\end{array} \right.\\
\left\{ \begin{array}{l}
2x - 8 < 0\\
15 - 3x < 0
\end{array} \right.
\end{array} \right.\\
\to \left[ \begin{array}{l}
\left\{ \begin{array}{l}
x > 4\\
5 > x
\end{array} \right.\\
\left\{ \begin{array}{l}
x < 4\\
x > 5
\end{array} \right.\left( l \right)
\end{array} \right.\\
\to 5 > x > 4\\
b)4x - 7 \ge 2x - 5\\
\to 2x \ge 2\\
\to x \ge 1\\
d)\left( {10 - 2x} \right)\left( {2x + 8} \right) \le 0\\
\to \left[ \begin{array}{l}
\left\{ \begin{array}{l}
10 - 2x \ge 0\\
2x + 8 \le 0
\end{array} \right.\\
\left\{ \begin{array}{l}
10 - 2x \le 0\\
2x + 8 \ge 0
\end{array} \right.
\end{array} \right.\\
\to \left[ \begin{array}{l}
\left\{ \begin{array}{l}
5 \ge x\\
x \le - 4
\end{array} \right.\\
\left\{ \begin{array}{l}
x \ge 5\\
x \ge - 4
\end{array} \right.
\end{array} \right.\\
\to \left[ \begin{array}{l}
x \le - 4\\
x \ge 5
\end{array} \right.
\end{array}\)
