# Math Help - Find Radius and Center of Sphere

1. ## Find Radius and Center of Sphere

Find radius and center of sphere.

3x^2 + 3y^2 + 3z^2 + 6x - 6y = 3

2. Hello,
Originally Posted by magentarita
Find radius and center of sphere.

3x^2 + 3y^2 + 3z^2 + 6x - 6y = 3
Do you know what the equation of a sphere is ?

$(x-x_0)^2+(y-y_0)^2+(z-z_0)^2=r^2$

Center $(x_0,y_0,z_0)$ and radius r.

Divide by 3 :
$x^2+y^2+z^2+2x-2y=1$

$(x^2+2x)+(y^2-2y)+z^2=1$

Complete the squares for the stuff in the brackets.

3. ## ok............

Originally Posted by Moo
Hello,

Do you know what the equation of a sphere is ?

$(x-x_0)^2+(y-y_0)^2+(z-z_0)^2=r^2$

Center $(x_0,y_0,z_0)$ and radius r.

Divide by 3 :
$x^2+y^2+z^2+2x-2y=1$

$(x^2+2x)+(y^2-2y)+z^2=1$

Complete the squares for the stuff in the brackets.
Very good notes and tips.