Equation for a circle I'm reading a book about Calculus on my own and am stuck at a problem, the problem is

There are two circles of radius $2$ that have centers on the line $x = 1$ and pass through the origin. Find their equations.

The equation for circle is $(x-h)^2 + (y-k)^2 = r^2$
Any hints will be really appreciated.
EDIT: Here is what I did. I drew a triangle from the origin and applied the pythogoras theorem to find the perpendicular, the hypotenuse being $2$ ($\text{radius} = 2$) and base $1$ (because $x = 1$), the value of y-coordinate is $\sqrt3$. Can anyone confirm if this is correct?

Rephrasing Dario's hint: the center of each circle is a point of distance $2$ from the origin with $x=1$. If the center is the point $(x,y)$ then $x=1$, and so you can solve for $y$ (remember, the distance between $(x,y)$ and $(0,0)$ is $2$).
