Đáp án:
$\begin{array}{l}
{x^3} - 7x - 6\\
= {x^3} - 3{x^2} + 3{x^2} - 9x + 2x - 6\\
= {x^2}\left( {x - 3} \right) + 3x\left( {x - 3} \right) + 2\left( {x - 3} \right)\\
= \left( {x - 3} \right)\left( {{x^2} + 3x + 2} \right)\\
= \left( {x - 3} \right)\left( {{x^2} + x + 2x + 2} \right)\\
= \left( {x - 3} \right)\left( {x + 2} \right)\left( {x + 1} \right)
\end{array}$