How do you find the center and radius of the ellipse with standard equation #x^2+6x+y^2-8y-11=0#?
First of all this is not an equation of an ellipse, but it is the equation of a circle (even if a circle can be defined as a "particular" ellipse).
The answer is:
It is possible to answer to the question in two ways.
The first, simplier, is remembering some formulas:
Equation of a circle:
In our case:
The second way is completing the squares: