Write the equation of the circle. Center at (4,2) and the circle passes through the point (-1,-1).

Question

Please help!

Answer 1

recall the equation of a circle with centre (h,k) and radius r is
(x-h)^2 + (y-k)^2 = r^2
so
(x-4)^2 + (y-2)^2 = r^2
but (-1,-1) lies on it
sub x=-1 and y=-1 to find r^2

let me know what you get.