How do you write the equation of a circle with center(3,-4)and radius of 7?
The unit circle, centered in the origin, has equation
This means that the squared lenght of the vector
Now we want to move the center as well, let's say that our new center is
With respect to these new coordinates, the circle is again centered in the origin, so it has equation
Plug back the definition, and you have the final result
Plugging your particular values, the equation is
If you like, you can do some manipulations: