Answer
vertices $(-4,0),(4,0),(0,-4),(0,4)$, focus $(0,0)$.
See graph.
Work Step by Step
1. Based on the given equation, we have $\frac{x^2}{16}+\frac{y^2}{16}=1$, with $a= b=4$, center $(0,0)$ and it is a circle, thus $c=\sqrt {a^2-b^2}=0$, vertices $(-4,0),(4,0),(0,-4),(0,4)$, focus $(0,0)$.
2. See graph.
