Question

Find the center and radius of the circle given by the equation
x^2+y^2 +2 x +12 y +28=0
I found the center, but idk how to find the r.

Answer 1

complete the square in x and y

\[(x^2 + 2x + ? ) +(y^2 +12y + ??) = -28 + ?^2 + ??^2\]

what do you need to add to both sets of brackets to get a perfect square