sphere equation

[Keego]

To find the radius and center of the sphere equation below, you need to first complete the square (or plug in the #'s to your calc) anyways, what's the radius and coords of the center of this sphere equation:

x^2+y^2+z^2+4x-2y-4z

 

[Ameesh]

if you know how to do it, why dont you just do it you need to get it into the form (x+?)^2+(y+?)^2+(z+?)^2

 

[MrBond]

You have to complete the square on that equation. Give me a minute and I'll se how rusty I am at doing that

Edit: (again) Mental note, don't do simple algebra in head)

 

[Atlantean]

Don't you group the variables?
x(x+4)+y(y-2)+z(z-4)
and then solve? I have no idea how it is actually done though.

 

[minendo]

(x+2)^2 + (y-1)^2 + (z-2)^2 = 9

I could be wrong in this cause I did just attempt to do it in my head and I am rusty at it.

 

[Random Variable]

(x^2+4x+4) + (y^2-2y+1)+(z^2-4z+4) = 4+1+4

(x+2)^2 +(y-1)^2 + (z-2)^2 = 9

center (-2,1,2)
radius 3

 

[Keego]

Thanks, we just had that in a quiz, glad to know I was right

 

[Ameesh]

<< Thanks, we just had that in a quiz, glad to know I was right >>



yeah right