Question

Knowing the given conditions, write the equation of the circle. Center at (4,2) and the circle passes through (-1,-1).
Please help!

Answer 1

I will assume you know that the equation of a circle with centre (h,k) and radius r is
(x-h)^2 + (y-k)^2 = r^2

then (x-4)^2 + (y-2)^2 = r^2
but (-1,-1) lies on it, so
(-1-4)^2 + (-1-2)^2 = r^2
r^2 = 34

(x-4)^2 + (y-2)^2 = 34

Answer 2

Thanks!