Answer
See the explanation below.
Work Step by Step
Standard form of a hyperbola is $\dfrac{x^2}{a^2}-\dfrac{y^2}{b^2}=1$
Standard form of of circles; $(x-a)^2+(y-b)^2=r^2$
Here, $r$ defines radius and $(a,b)$ defines center.
When we compare the standard form for both a circle and ellipse we can only see the difference of the signs of the coefficients of the squared variable $x^2$ and $y^2$.
For same coefficients it defines a circle and unequal coefficients define an ellipse.
