$\begin{array}{l}\phantom{\phantom{;}a^{2}+3a\phantom{;}-1;}{\phantom{;}2a^{2}+a\phantom{;}-1\phantom{;}\phantom{;}}\\\phantom{;}a^{2}+3a\phantom{;}-1\overline{\smash{)}\phantom{;}2a^{4}+7a^{3}\phantom{-;x^n}+2a\phantom{;}-1\phantom{;}\phantom{;}}\\\phantom{\phantom{;}a^{2}+3a\phantom{;}-1;}\underline{-2a^{4}-6a^{3}+2a^{2}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{-2a^{4}-6a^{3}+2a^{2};}\phantom{;}a^{3}+2a^{2}+2a\phantom{;}-1\phantom{;}\phantom{;}\\\phantom{\phantom{;}a^{2}+3a\phantom{;}-1-;x^n;}\underline{-a^{3}-3a^{2}+a\phantom{;}\phantom{-;x^n}}\\\phantom{;-a^{3}-3a^{2}+a\phantom{;}-;x^n;}-a^{2}+3a\phantom{;}-1\phantom{;}\phantom{;}\\\phantom{\phantom{;}a^{2}+3a\phantom{;}-1-;x^n-;x^n;}\underline{\phantom{;}a^{2}+3a\phantom{;}-1\phantom{;}\phantom{;}}\\\phantom{;;\phantom{;}a^{2}+3a\phantom{;}-1\phantom{;}\phantom{;}-;x^n-;x^n;}\phantom{;}6a\phantom{;}-2\phantom{;}\phantom{;}\\\end{array}$

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