Hi
circle whose diameter has endpoints of (3, 0) and (7, 10)
(3, 0) and 
(7, 10) Midpoint is   (5,5)             |  ( 
, 
)
(3, 0) and 
(7, 10  D = sqrt( (-4)^2 + (-10)^2))        |  D = 
 
  D = sqrt(116) = 2sqrt(29) and r = sqrt(29)
 Standard Form of an Equation of a Circle is 
where Pt(h,k) is the center and r is the radius
   (x-5)^2 + (y-5)^2 = 29