Precalculus (6th Edition) Blitzer

Assume that there was a hyperbola with the given conditions. We have $c=2, a=3$ and thus $b=\sqrt {c^2-a^2}=\sqrt {2^2-3^2}=\sqrt {-5}$. So, we can not obtain a real value for $b$. This means that the original hyperbola does not exist.