Like the other one I helped with, find the center of the circle by finding the midpoint of the diameter points:
Midpoint = (-2+2 /2 ), -1+1 /2) = (0,0)
The center of the circle is at (0,0)
Now find the radius using one of the end points and the center:
Radius = √((-2-0)^2 + (-1-0)^2) = √5
The equation of a circle is written as (x-h)^2 + (Y-k)^2 = r^2
H and K are the center points of the circle and r is the radius. Replace the letters with their values:
(X-0)^2 + (y-0)^2 = (√5)^2
Simplify to get:
(X-0)^2 + (y-0)^2 = 5