$\begin{array}{l}\phantom{\phantom{;}x^{3}+3;}{\phantom{;}x^{2}+2x\phantom{;}-1\phantom{;}\phantom{;}}\\\phantom{;}x^{3}+3\overline{\smash{)}\phantom{;}x^{5}+2x^{4}-x^{3}\phantom{-;x^n}\phantom{-;x^n}+2\phantom{;}\phantom{;}}\\\phantom{\phantom{;}x^{3}+3;}\underline{-x^{5}\phantom{-;x^n}\phantom{-;x^n}-3x^{2}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{-x^{5}-3x^{2};}\phantom{;}2x^{4}-x^{3}-3x^{2}\phantom{-;x^n}+2\phantom{;}\phantom{;}\\\phantom{\phantom{;}x^{3}+3-;x^n;}\underline{-2x^{4}\phantom{-;x^n}\phantom{-;x^n}-6x\phantom{;}\phantom{-;x^n}}\\\phantom{;-2x^{4}-6x\phantom{;}-;x^n;}-x^{3}-3x^{2}-6x\phantom{;}+2\phantom{;}\phantom{;}\\\phantom{\phantom{;}x^{3}+3-;x^n-;x^n;}\underline{\phantom{;}x^{3}\phantom{-;x^n}\phantom{-;x^n}+3\phantom{;}\phantom{;}}\\\phantom{;;\phantom{;}x^{3}+3\phantom{;}\phantom{;}-;x^n-;x^n;}-3x^{2}-6x\phantom{;}+5\phantom{;}\phantom{;}\\\end{array}$

$x^{2}+2x-1+\frac{-3x^{2}-6x+5}{x^3+3}$