$\begin{array}{l}\phantom{\phantom{;}3x\phantom{;}+1;}{\phantom{;}x^{2}-2x\phantom{;}+4\phantom{;}\phantom{;}}\\\phantom{;}3x\phantom{;}+1\overline{\smash{)}\phantom{;}3x^{3}-5x^{2}+10x\phantom{;}-3\phantom{;}\phantom{;}}\\\phantom{\phantom{;}3x\phantom{;}+1;}\underline{-3x^{3}-x^{2}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{-3x^{3}-x^{2};}-6x^{2}+10x\phantom{;}-3\phantom{;}\phantom{;}\\\phantom{\phantom{;}3x\phantom{;}+1-;x^n;}\underline{\phantom{;}6x^{2}+2x\phantom{;}\phantom{-;x^n}}\\\phantom{;\phantom{;}6x^{2}+2x\phantom{;}-;x^n;}\phantom{;}12x\phantom{;}-3\phantom{;}\phantom{;}\\\phantom{\phantom{;}3x\phantom{;}+1-;x^n-;x^n;}\underline{-12x\phantom{;}-4\phantom{;}\phantom{;}}\\\phantom{;;-12x\phantom{;}-4\phantom{;}\phantom{;}-;x^n-;x^n;}-7\phantom{;}\phantom{;}\\\end{array}$

$x^{2}-2x+4+\frac{-7}{3x+1}$