Đáp án:
$\begin{array}{l}
\frac{{{x^3} + 5{x^2} - 4x - 20}}{{{x^2} + 3x - 10}}\\
= \frac{{{x^2}\left( {x + 5} \right) - 4\left( {x + 5} \right)}}{{{x^2} - 2x + 5x - 10}}\\
= \frac{{\left( {x + 5} \right)\left( {{x^2} - 4} \right)}}{{\left( {x - 2} \right)x + 5\left( {x - 2} \right)}}\\
= \frac{{\left( {x + 5} \right)\left( {x - 2} \right)\left( {x + 2} \right)}}{{\left( {x - 2} \right)\left( {x + 5} \right)}}\\
= x + 2
\end{array}$
