$\dfrac{3x - 6}{2x + 6}$ là số nguyên
$\Leftrightarrow 3x - 6 \vdots 2x + 6$
$\Leftrightarrow 2(3x - 6) \vdots 3(2x + 6)$
$\Leftrightarrow 6x - 12 \vdots 6x + 18$
$\Leftrightarrow 6x + 18 - 30 \vdots 6x + 18$
$\Leftrightarrow 30 \vdots 6x + 18$
$\Leftrightarrow 6x + 18 \in Ư\left ( 30 \right )$
$\Leftrightarrow 6x + 18 \in \left \{ -30; -15; -10; -5; -6; -3; -2; -1; 1; 2; 3; 5; 6; 10; 15; 30 \right \}$
$\Leftrightarrow x \in \left \{ -8; -4; -2; 2 \right \}$
