Đáp án:
\(\begin{array}{l}
A)\left[ \begin{array}{l}
x \ge \sqrt 5 \\
x \le - \sqrt 5
\end{array} \right.\\
C)\left[ \begin{array}{l}
x \ge \sqrt {15} \\
x \le - \sqrt {15}
\end{array} \right.\\
E)\left[ \begin{array}{l}
x \ge 2\\
x \le 1
\end{array} \right.\\
G)\left[ \begin{array}{l}
x \ge 4\\
x \le - 3
\end{array} \right.\\
I)\left[ \begin{array}{l}
x \ge \dfrac{4}{3}\\
x \le 1
\end{array} \right.
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
A)DK:{x^2} - 5 \ge 0\\
\to {x^2} \ge 5\\
\to \left[ \begin{array}{l}
x \ge \sqrt 5 \\
x \le - \sqrt 5
\end{array} \right.\\
C)DK:{x^2} - 15 \ge 0\\
\to {x^2} \ge 15\\
\to \left[ \begin{array}{l}
x \ge \sqrt {15} \\
x \le - \sqrt {15}
\end{array} \right.\\
E)DK:\left( {x - 1} \right)\left( {x - 2} \right) \ge 0\\
\to \left[ \begin{array}{l}
\left\{ \begin{array}{l}
x - 1 \ge 0\\
x - 2 \ge 0
\end{array} \right.\\
\left\{ \begin{array}{l}
x - 1 \le 0\\
x - 2 \le 0
\end{array} \right.
\end{array} \right.\\
\to \left[ \begin{array}{l}
x \ge 2\\
x \le 1
\end{array} \right.\\
G)DK:{x^2} - x - 12 \ge 0\\
\to \left( {x - 4} \right)\left( {x + 3} \right) \ge 0\\
\to \left[ \begin{array}{l}
\left\{ \begin{array}{l}
x - 4 \ge 0\\
x + 3 \ge 0
\end{array} \right.\\
\left\{ \begin{array}{l}
x - 4 \le 0\\
x + 3 \le 0
\end{array} \right.
\end{array} \right.\\
\to \left[ \begin{array}{l}
x \ge 4\\
x \le - 3
\end{array} \right.\\
I)DK:3{x^2} - 7x + 4 \ge 0\\
\to \left( {3x - 4} \right)\left( {x - 1} \right) \ge 0\\
\to \left[ \begin{array}{l}
x \ge \dfrac{4}{3}\\
x \le 1
\end{array} \right.
\end{array}\)
