$\begin{array}{l}\phantom{\phantom{;}2x^{2}-5;}{-6x^{2}-4x\phantom{;}-15\phantom{;}\phantom{;}}\\\phantom{;}2x^{2}-5\overline{\smash{)}-12x^{4}-8x^{3}\phantom{-;x^n}+3x\phantom{;}+9\phantom{;}\phantom{;}}\\\phantom{\phantom{;}2x^{2}-5;}\underline{\phantom{;}12x^{4}\phantom{-;x^n}-30x^{2}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{\phantom{;}12x^{4}-30x^{2};}-8x^{3}-30x^{2}+3x\phantom{;}+9\phantom{;}\phantom{;}\\\phantom{\phantom{;}2x^{2}-5-;x^n;}\underline{\phantom{;}8x^{3}\phantom{-;x^n}-20x\phantom{;}\phantom{-;x^n}}\\\phantom{;\phantom{;}8x^{3}-20x\phantom{;}-;x^n;}-30x^{2}-17x\phantom{;}+9\phantom{;}\phantom{;}\\\phantom{\phantom{;}2x^{2}-5-;x^n-;x^n;}\underline{\phantom{;}30x^{2}\phantom{-;x^n}-75\phantom{;}\phantom{;}}\\\phantom{;;\phantom{;}30x^{2}-75\phantom{;}\phantom{;}-;x^n-;x^n;}-17x\phantom{;}-66\phantom{;}\phantom{;}\\\end{array}$

$-6x^{2}-4x-15+\frac{-17x-66}{2x^2-5}$