Answer:
(x -a)^2 + y^2 = 2a^2
Explanation:
The equation of a circle with center (h, k) and radius r is ...
(x -h)^2 +(y -k)^2 = r^2
Here r^2 is the square of the distance between the center and the point on the circle. That can be found using the distance formula:
d^2 = r^2 = (x2-x1)^2 +(y2 -y1)^2 = (0-a)^2 +(-a-0)^2 = 2a^2
Filling in the above formula with (h, k) = (a, 0) and r^2 = 2a^2, we find the equation to be ...
(x -a)^2 +y^2 = 2a^2