The equation of the circle that you are looking for is x^2 + y^2 = 100.
You can find this by using the base formula for a circle:
(x - x1)^2 + (y - y1)^2 = r^2
In which x1 is the x-coordinate of the origin, y1 is the y-coordinate of the origin, and r is the radius. So we put in the values we know and simplify.
(x -0)^2 + (y - 0)^2 = 10^2
x^2 + y^2 = 100
