Đáp án:
$\begin{array}{l}
- 10{x^2} + {x^4} - 9\\
= {x^4} - 10{x^2} - 9\\
= \left( {{x^4} - 2{x^3} - 3{x^2}} \right) + \left( {2{x^3} - 4{x^2} - 6x} \right)\\
- 3{x^2} + 6x + 9 - 18\\
= {x^2}\left( {{x^2} - 2x - 3} \right) + 2x\left( {{x^2} - 2x - 3} \right)\\
- 3\left( {{x^2} - 2x - 3} \right) - 18\\
= \left( {{x^2} - 2x - 3} \right)\left( {{x^2} + 2x - 3} \right) - 18\\
\Rightarrow \left( { - 10{x^2} + {x^4} - 9} \right):\left( {{x^2} - 2x - 3} \right)\\
= {x^2} + 2x - 3\,dư\, - 18
\end{array}$