Question

The point (-1,2) lies on a circle whose center is at (-4,1) . Find an equation of this circle.

Answer 1

first find the distance. that is the radius of the circle. distance is
\[\sqrt{(-1+4)^2+(2-1)^2}\]
\[\sqrt{3^2+1^2}=\sqrt{10}\]
then just write
\[(x+4)^2+(y-1)^2=10\]