Question

Find the standard form for the equation of a circle
(x−h)^2+(y−k)^2=r^2
with a diameter that has endpoints (−8,−10) and (5,−4).
Find the h= -1.5
k= -7
r=?
I do not understand how to find the radius.

Answer 1

just plug in either of the points. They must satisfy the equation, so if we pick (-8,-10),

(-8+1.5)^2 + (-10+7)^2 = r^2