Finding the Equations of a Circle provided a point and the radius So I tried googling the exact question and I never found the solution. This is homework so I really don't want to know the answer but how to arrive at the answer.
The question that was given was "What are the equations of the circles tangent to the x-axis of radius 4 and whose center is at (-2,y)?"
From the given and a little graphing, I found that (-2,0) would be the point where the circle is tangent to the x-axis. Am I correct?
if I am correct, then I have 2 given pieces of information which is the radius of 4 and a point as well as the x-value of the center. 
With all the equations my professor given me, I still don't know how to solve to get the center. Can someone point me to the right direction? 
thanks.

Hint:
You have correctly found the point $(-2,0)$ where the circle is tangent to the $x$ axis. Now you know the radius $4$ and you also know that the radius  is orthogonal to the tangent. So, where can be the center of the circle?
