Đáp án:
\(\begin{array}{l}
n) - \dfrac{1}{3} \ge x\\
o)4 > x > 0
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
n)DK:\left\{ \begin{array}{l}
- x + 3 \ge 0\\
- 3x - 1 \ge 0
\end{array} \right.\\
\to \left\{ \begin{array}{l}
3 \ge x\\
- \dfrac{1}{3} \ge x
\end{array} \right.\\
\to - \dfrac{1}{3} \ge x\\
o)DK:{x^2} - 4x < 0\\
\to x\left( {x - 4} \right) < 0\\
\to \left[ \begin{array}{l}
\left\{ \begin{array}{l}
x > 0\\
x - 4 < 0
\end{array} \right.\\
\left\{ \begin{array}{l}
x < 0\\
x - 4 > 0
\end{array} \right.
\end{array} \right.\\
\to \left[ \begin{array}{l}
\left\{ \begin{array}{l}
x > 0\\
x < 4
\end{array} \right.\\
\left\{ \begin{array}{l}
x < 0\\
x > 4
\end{array} \right.\left( l \right)
\end{array} \right.\\
\to 4 > x > 0
\end{array}\)
