1) $y = \dfrac{x +1}{x -1}$
$y$ xác định $\Leftrightarrow x - 1 \ne 0 \Leftrightarrow x \ne 1$
$\Rightarrow TXD: D = \Bbb R\backslash\left\{1\right\}$
Hoặc $D = (-\infty;1)\cup (1;+\infty)$
2) $y = \dfrac{x -3}{2x - 2}$
$y$ xác định $\Leftrightarrow 2x - 2 \ne 0 \Leftrightarrow x \ne 1$
$\Rightarrow TXD: D =\Bbb R\backslash\left\{1\right\}$
Hoặc $D = (-\infty;1)\cup (1;+\infty)$
3) $y= \dfrac{x +2}{(x +3)^2}$
$y$ xác định $\Leftrightarrow (2x + 3)^2 \ne 0 \Leftrightarrow x \ne -\dfrac{3}{2}$
$\Rightarrow TXD: D = \Bbb R \backslash\left\{-\dfrac{3}{2}\right\}$
Hoặc $D = \left(-\infty;-\dfrac{3}{2}\right)\cup \left(-\dfrac{3}{2};+\infty\right)$
4) $y = \dfrac{3x -1}{2x -2}$
$y$ xác định $\Leftrightarrow 2x - 2 \ne 0 \Leftrightarrow x \ne 1$
$\Rightarrow TXD: D =\Bbb R\backslash\left\{1\right\}$
Hoặc $D = (-\infty;1)\cup (1;+\infty)$
