$\begin{array}{l}\phantom{\phantom{;}x\phantom{;}+3;}{\phantom{;}3x^{2}-21x\phantom{;}+66\phantom{;}\phantom{;}}\\\phantom{;}x\phantom{;}+3\overline{\smash{)}\phantom{;}3x^{3}-12x^{2}+3x\phantom{;}-1\phantom{;}\phantom{;}}\\\phantom{\phantom{;}x\phantom{;}+3;}\underline{-3x^{3}-9x^{2}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{-3x^{3}-9x^{2};}-21x^{2}+3x\phantom{;}-1\phantom{;}\phantom{;}\\\phantom{\phantom{;}x\phantom{;}+3-;x^n;}\underline{\phantom{;}21x^{2}+63x\phantom{;}\phantom{-;x^n}}\\\phantom{;\phantom{;}21x^{2}+63x\phantom{;}-;x^n;}\phantom{;}66x\phantom{;}-1\phantom{;}\phantom{;}\\\phantom{\phantom{;}x\phantom{;}+3-;x^n-;x^n;}\underline{-66x\phantom{;}-198\phantom{;}\phantom{;}}\\\phantom{;;-66x\phantom{;}-198\phantom{;}\phantom{;}-;x^n-;x^n;}-199\phantom{;}\phantom{;}\\\end{array}$

$3x^{2}-21x+66+\frac{-199}{x+3}$