$\begin{array}{l}\phantom{-x\phantom{;}+3;}{-4x^{2}-6x\phantom{;}-20\phantom{;}\phantom{;}}\\-x\phantom{;}+3\overline{\smash{)}\phantom{;}4x^{3}-6x^{2}+2x\phantom{;}-9\phantom{;}\phantom{;}}\\\phantom{-x\phantom{;}+3;}\underline{-4x^{3}+12x^{2}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{-4x^{3}+12x^{2};}\phantom{;}6x^{2}+2x\phantom{;}-9\phantom{;}\phantom{;}\\\phantom{-x\phantom{;}+3-;x^n;}\underline{-6x^{2}+18x\phantom{;}\phantom{-;x^n}}\\\phantom{;-6x^{2}+18x\phantom{;}-;x^n;}\phantom{;}20x\phantom{;}-9\phantom{;}\phantom{;}\\\phantom{-x\phantom{;}+3-;x^n-;x^n;}\underline{-20x\phantom{;}+60\phantom{;}\phantom{;}}\\\phantom{;;-20x\phantom{;}+60\phantom{;}\phantom{;}-;x^n-;x^n;}\phantom{;}51\phantom{;}\phantom{;}\\\end{array}$

$-4x^{2}-6x-20+\frac{51}{3-x}$