Giải thích các bước giải:
\(\begin{array}{l}
a.DK:x \ne \left\{ { - 3;2} \right\}\\
A = \frac{{{x^2} - 4 - 5 - x - 3}}{{\left( {x + 3} \right)\left( {x - 2} \right)}}\\
= \frac{{{x^2} - x - 12}}{{\left( {x + 3} \right)\left( {x - 2} \right)}} = \frac{{\left( {x - 4} \right)\left( {x + 3} \right)}}{{\left( {x + 3} \right)\left( {x - 2} \right)}}\\
= \frac{{x - 4}}{{x - 2}}\\
b.A > 0\\
\Leftrightarrow \frac{{x - 4}}{{x - 2}} > 0\\
\Leftrightarrow \left[ \begin{array}{l}
\left\{ \begin{array}{l}
x - 4 > 0\\
x - 2 > 0
\end{array} \right.\\
\left\{ \begin{array}{l}
x - 4 < 0\\
x - 2 < 0
\end{array} \right.
\end{array} \right. \to \left[ \begin{array}{l}
x > 4\\
x < 2
\end{array} \right.
\end{array}\)
