Cal III/ Multi-V (vector notation troubles)

[The_Chromer]

Homework Statement

Given vector A = i + j - k and vector B= i - j + k, calculate ||3A-B||.

My work can be found here (I am not literate in Latex markups):
http://img714.imageshack.us/img714/732/sixhomeworkproblems001.jpg

I am unfamiliar with the notation of the double bars surrounding this vector combination. I think, and I say that very loosely, that it means to find the normal vector to the plane. If I could get some clarification for that, then I don't think the problem should be too difficult.

Homework Equations

Uncertain of problem notation.

The Attempt at a Solution

http://img823.imageshack.us/img823/8554/attempt001.jpg

 

[Whitishcube]

You're really close. All you have to do is find the magnitude of that vector. The equation for that is the square root of the sum of all of its components squared.
Sqrt(a^2+b^2+c^2).

 

[The_Chromer]

Wow. So all the question asks for is the magnitude?

sqrt(36)=6