$\begin{array}{l}\phantom{\phantom{;}2x\phantom{;}-1;}{\phantom{;}3x^{3}+14x^{2}+16x\phantom{;}-4\phantom{;}\phantom{;}}\\\phantom{;}2x\phantom{;}-1\overline{\smash{)}\phantom{;}6x^{4}+25x^{3}+18x^{2}-24x\phantom{;}+4\phantom{;}\phantom{;}}\\\phantom{\phantom{;}2x\phantom{;}-1;}\underline{-6x^{4}+3x^{3}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{-6x^{4}+3x^{3};}\phantom{;}28x^{3}+18x^{2}-24x\phantom{;}+4\phantom{;}\phantom{;}\\\phantom{\phantom{;}2x\phantom{;}-1-;x^n;}\underline{-28x^{3}+14x^{2}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{;-28x^{3}+14x^{2}-;x^n;}\phantom{;}32x^{2}-24x\phantom{;}+4\phantom{;}\phantom{;}\\\phantom{\phantom{;}2x\phantom{;}-1-;x^n-;x^n;}\underline{-32x^{2}+16x\phantom{;}\phantom{-;x^n}}\\\phantom{;;-32x^{2}+16x\phantom{;}-;x^n-;x^n;}-8x\phantom{;}+4\phantom{;}\phantom{;}\\\phantom{\phantom{;}2x\phantom{;}-1-;x^n-;x^n-;x^n;}\underline{\phantom{;}8x\phantom{;}-4\phantom{;}\phantom{;}}\\\phantom{;;;\phantom{;}8x\phantom{;}-4\phantom{;}\phantom{;}-;x^n-;x^n-;x^n;}\\\end{array}$

$3x^{3}+14x^{2}+16x-4$