Let $$f(x) = \frac{9 x^2 + 5 x + 6}{2x^2 + 12 x - 54}.$$ Find the horizontal and vertical asymptotes of $f(x)$. If there are no asymptotes of a given type, enter none. If there are more than one of a given type, list them separated by commas.

Horizontal asymptote(s): $y$ =

Vertical asymptote(s): $x$ =