Đáp án:
\(\begin{array}{l}
a)\left\{ \begin{array}{l}
x \ne \pm 3\\
\dfrac{5}{2} \ge x
\end{array} \right.\\
d)\left[ \begin{array}{l}
x \ge 3\\
x \le 1
\end{array} \right.\\
b)8 \ge x \ge 2\\
e)x > - 3\\
c)3 \ge x \ge - 1\\
f)5 > x \ge - 2\\
g)\left[ \begin{array}{l}
x \ge 1\\
x < - 2
\end{array} \right.
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a)DK:\left\{ \begin{array}{l}
{x^2} - 9 \ne 0\\
5 - 2x \ge 0
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x \ne \pm 3\\
\dfrac{5}{2} \ge x
\end{array} \right.\\
d)DK:\left[ \begin{array}{l}
\left\{ \begin{array}{l}
x - 1 \ge 0\\
x - 3 \ge 0
\end{array} \right.\\
\left\{ \begin{array}{l}
x - 1 \le 0\\
x - 3 \le 0
\end{array} \right.
\end{array} \right. \to \left[ \begin{array}{l}
x \ge 3\\
x \le 1
\end{array} \right.\\
b)DK:\left\{ \begin{array}{l}
2x - 4 \ge 0\\
8 - x \ge 0
\end{array} \right.\\
\to 8 \ge x \ge 2\\
e)DK:x + 3 > 0\\
\to x > - 3\\
c)DK:\left\{ \begin{array}{l}
4 - x \ge 0\\
x + 1 > 0\\
9 - {x^2} \ge 0
\end{array} \right.\\
\to \left\{ \begin{array}{l}
4 \ge x > - 1\\
3 \ge x \ge - 3
\end{array} \right.\\
\to 3 \ge x \ge - 1\\
f)DK:\left\{ \begin{array}{l}
x + 2 \ge 0\\
5 - x > 0
\end{array} \right.\\
\to 5 > x \ge - 2\\
g)DK:\left[ \begin{array}{l}
\left\{ \begin{array}{l}
x - 1 \ge 0\\
x + 2 > 0
\end{array} \right.\\
\left\{ \begin{array}{l}
x - 1 \le 0\\
x + 2 < 0
\end{array} \right.
\end{array} \right.\\
\to \left[ \begin{array}{l}
x \ge 1\\
x < - 2
\end{array} \right.
\end{array}\)
