Find an equation for the hyperbola whose graph has vertices $(\pm 2,0)$ and asymptotes $y=\pm 4 x$.
The equation has the form (input a or b) :
(a) $\frac{x^2}{a^2}-\frac{y^2}{b^2}=1$, or (b) $\frac{y^2}{a^2}-\frac{x^2}{b^2}=1$;
the positive numbers $a=$ and $b=$ .