If you have not encountered the term "orthogonal circles" before you can use this environment to figure out what the term could mean.
The black dots fix the centers of the circles - red & green dots fix the radii of the circles
If you add a fixed length, say d, to each of the radii of orthogonal circles and the distance between the centers, do the circles remain orthogonal?
[always, sometimes, never]
If you multiply each of the radii of orthogonal circles and the distance between the centers by the same amount, say a, do the circles remain orthogonal?
[always, sometimes, never]
Write an equation or a set of equations that relate the positions of the centers, the size of the radii and the location of the point(s) of intersection of the two circles.