The equation of a circle is (x-h)^2 + (y-k)^2 = r^2
to find (h,k), you find the middle of the circle, in this scenario you do so by finding the middle of the diameter, a line that goes through the center of the circle.
To find the X value of the midpoint, add both x values together and divide by 2 and repeat for y
-13 + -1 = -14 -14/2 =-7
10+ -6 = 4 4/2 = 2
therefore (h,k) = ( -7, 2 )
Next plug these values in the equation of a circle
(x-h)^2 + (y-k)^2 = r^2
becomes
(x- (-7)) ^2 + (y-(2)) ^2 = r^2
to find r, use the distance formula to find the length of the diameter, 20, and divide by 2
