write the equation of a circle with diameter endpoints of (13, -1) and (-15,9)

let
A (13,-1)
B (-15,9)

we know that
the distance AB is the diameter
and
the midpoint AB is the center
step 1
find the distance AB
d=√[(y2-y1)²+(x2-x1)²]------> d=√[(9+1)²+(-15-13)²]----> d=√[100+784]
d=√884 units
diameter=√884 units
r=√884/2  units

step 2
find the midpoint AB
Mx=(13-15)/2----> -1
My=(9-1)/2-------> 4
the center of the circle is (-1,4)

step 3
find the equation of a circle
(x-h)²+(y-k)²=r²--------> (x+1)²+(y-4)²=(√884/2)²
(x+1)²+(y-4)²=221