Question

Find the center and radius of the circle whose equation is x^2+y^2+4x+12y =-15

Answer 1

center: (-2,-6)

radius: 5

Explanation:

You have to complete the square again. This time the x's and the y's both need work. So first, organize. Put the x's together and put the y's together. Leave a little room to work. Take the x term and the y term and CUT them in HALF and Square 'em. That is what you add in to complete the square. Add the same thing to both sides.

see image.