Hey,

I've got this equation and I was wondering what the steps are to get the answer becuase I got something different to the answer.

x^2 + y^2 + z^2 + 4x − 6y + 2z + 6 = 0

Complete the square to find the origin and the radius

I got the origin all right but my radius came out to be sqrt(20) and the answer says it's sqrt(8).

If someone could explain that would be great.