Đáp án:
$\begin{array}{l}
+ )\frac{5}{{3{x^3} - 12x}}\\
= \frac{5}{{3x\left( {{x^2} - 4} \right)}}\\
= \frac{{5.2.\left( {x + 3} \right)}}{{6x\left( {x + 2} \right)\left( {x - 2} \right)\left( {x + 3} \right)}}\\
= \frac{{10x + 30}}{{6x\left( {x + 2} \right)\left( {x - 2} \right)\left( {x + 3} \right)}}\\
+ )\frac{3}{{\left( {2x + 4} \right)\left( {x + 3} \right)}}\\
= \frac{3}{{2\left( {x + 2} \right)\left( {x + 3} \right)}}\\
= \frac{{3.3x\left( {x - 2} \right)}}{{6x\left( {x + 2} \right)\left( {x - 2} \right)\left( {x + 3} \right)}}\\
= \frac{{9{x^2} - 18x}}{{6x\left( {x + 2} \right)\left( {x - 2} \right)\left( {x + 3} \right)}}
\end{array}$
