(a) The vertical asymptote of the curve $$y=\frac{-6 x^3}{x +2}$$ is given by $x=$ .


(b) The horizontal asymptotes of the curve $$y=\frac{5 x}{(x^4 +1)^{\frac{1}{4}}}$$ is given by $y=$ and $y=$ (enter these two values in ascending order).