Hello again so... upon trying to find the center and radius of this equation: x^2+y^2-6x-8y+16=0

I find that the center is (3,4)

When finding the radius and inputing so many forms out of fustration I keep on coming up with 9 ! I have to submit my homework online so it tells me automatically if it is right or wrong and so far it is wrong. I literally asked a question like this 1-2 days ago and I guess I still don't understand what to do when I get to this point. HELP !

Question

Hello again so... upon trying to find the center and radius of this equation: x^2+y^2-6x-8y+16=0 

I find that the center is (3,4)

When finding the radius and inputing so many forms out of fustration I keep on coming up with 9 ! I have to submit my homework online so it tells me automatically if it is right or wrong and so far it is wrong. I literally asked a question like this 1-2 days ago and I guess I still don't understand what to do when I get to this point. HELP !

anonymous · Answer

in $$x^2+y^2+2gx+2fy+c=0$$
$$center~ is~(-g,-h) ~and~radius=\sqrt{g^2+f^2-c}$$

anonymous · Answer

were you completing the square or using that formula?

anonymous · Answer

Thank you so much..... I make things overly complicated -.- but thanks again ! :D @surjithayer

anonymous · Answer

I was completing the square but I got it now, thank you for your time ! @peachpi 《 i like the username by the way ^.^