a) ĐK \(x + 2 \ne 0 \Leftrightarrow x \ne - 2\)
TXĐ: \(D = \mathbb{R}\backslash \left\{ { - 2} \right\}\)
b) ĐK \(2x - 4 \ge 0 \Leftrightarrow x \ge 2\)
TXĐ: \(D = \left[ {2; + \infty } \right)\)
c) ĐK \(x - 4 > 0 \Leftrightarrow x > 4\)
TXĐ: \(\left( {4; + \infty } \right)\)
d) ĐK \(\left\{ \begin{array}{l}3 - x > 0\\x - 1 \ne 0\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}x < 3\\x \ne 1\end{array} \right.\)
TXĐ: \(D = \left( { - \infty ;3} \right)\backslash \left\{ 1 \right\}\)
e) ĐK \({x^2} + 2x - 3 \ne 0 \Leftrightarrow \left( {x - 1} \right)\left( {x + 3} \right) \ne 0\) \( \Leftrightarrow \left\{ \begin{array}{l}x - 1 \ne 0\\x + 3 \ne 0\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}x \ne 1\\x \ne - 3\end{array} \right.\)
TXĐ: \(D = \mathbb{R}\backslash \left\{ {1; - 3} \right\}\)
f) ĐK \(\left\{ \begin{array}{l}2 - 4x \ge 0\\3x + 9 \ge 0\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}x \le \dfrac{1}{2}\\x \ge - 3\end{array} \right. \Leftrightarrow - 3 \le x \le \dfrac{1}{2}\)
TXĐ \(D = \left[ { - 3;\dfrac{1}{2}} \right]\)
g) ĐK \(\left\{ \begin{array}{l}2x - 3 \ge 0\\3 - x > 0\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}x \ge \dfrac{3}{2}\\x < 3\end{array} \right. \Leftrightarrow \dfrac{3}{2} \le x < 3\)
TXĐ \(D = \left[ {\dfrac{3}{2};3} \right)\)
