I think the radius is 4 so
(x-4)^2 + (y-1)^2 = 4^2

how did you get the 4..thank you
it touches the y axis so i think that the circle is tangent to the y axis. Since the center is located at (4, 1) and it touches the y axis, it's like saying 4-0 haha. I don't know if you get my explanation XD
i got it...a very big thanks