Originally Posted by
Principia11 I am trying to teach myself analytic geometry and ran across a book with lots of problems but unfortunately it does not have a lot of answers. So can you guys please check my work and tell me if I got anything wrong (and where I got something wrong).
Thanks!
1. "Find the center and radius of each of the following circles"
x^2 + y^2 - 4x + 6y = 12
I rearranged the terms, added parentheses and then added the squaring terms:
(x^2 - 4x +4) + (y + 6y + 9) = 12 + 4 + 9
then added 9 + 4 to 12, and then arranged the equation in the squared form to get
(x-2)^2 + (y-(-3))^2 = 25
so r = sqrt(25)
and the center is: 2,-3
Please check my work