Hey, i'm trying to solve this and im confused by the 2x and 2y. How do I treat this problem?

Thanks guys.

- Sep 11th 2008, 09:03 AMbigitmeFind the coordinates of the center and the radius of the circle
Hey, i'm trying to solve this and im confused by the 2x and 2y. How do I treat this problem?

Thanks guys. - Sep 11th 2008, 09:09 AMChris L T521
$\displaystyle 2x^2+2y^2+18x+4=0$

First divide the equation through by 2:

$\displaystyle x^2+y^2+9x+2=0$

Subtract 2 from both sides:

$\displaystyle x^2+y^2+9x=-2$

Group the x terms together:

$\displaystyle (x^2+9x)+y^2=-2$

Complete the square:

$\displaystyle \left(x^2+9x+\tfrac{81}{4}\right)+y^2=-2+\tfrac{81}{4}$

$\displaystyle \left(x+\tfrac{9}{2}\right)^2+y^2=\tfrac{77}{4}$

Thus, the center of the circle is ........

The radius of the circle is ........

I hope this helps! (Sun)

--Chris - Sep 11th 2008, 09:13 AMCaptainBlack
- Sep 11th 2008, 09:15 AMmasters
- Sep 11th 2008, 09:20 AMChris L T521