$\begin{array}{l}\phantom{\phantom{;}x\phantom{;}+4;}{\phantom{;}3x^{2}-20x\phantom{;}+86\phantom{;}\phantom{;}}\\\phantom{;}x\phantom{;}+4\overline{\smash{)}\phantom{;}3x^{3}-8x^{2}+6x\phantom{;}+8\phantom{;}\phantom{;}}\\\phantom{\phantom{;}x\phantom{;}+4;}\underline{-3x^{3}-12x^{2}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{-3x^{3}-12x^{2};}-20x^{2}+6x\phantom{;}+8\phantom{;}\phantom{;}\\\phantom{\phantom{;}x\phantom{;}+4-;x^n;}\underline{\phantom{;}20x^{2}+80x\phantom{;}\phantom{-;x^n}}\\\phantom{;\phantom{;}20x^{2}+80x\phantom{;}-;x^n;}\phantom{;}86x\phantom{;}+8\phantom{;}\phantom{;}\\\phantom{\phantom{;}x\phantom{;}+4-;x^n-;x^n;}\underline{-86x\phantom{;}-344\phantom{;}\phantom{;}}\\\phantom{;;-86x\phantom{;}-344\phantom{;}\phantom{;}-;x^n-;x^n;}-336\phantom{;}\phantom{;}\\\end{array}$

$3x^{2}-20x+86+\frac{-336}{x+4}$