Thread: Proof with vectors

hi,

I've the following proof with vectors that I don't know how to prove it. Can anyone help me?

1 - The problem is:

For which alpha belongs R, does alpha(1,1,1)^T - (3,2,4)^T have length sqroot(6)?

R - is the real numbers domain.
The matrix showed are transposed.
alpha - is the greek letter


2 - How do I put math characters in the posts?


Thanks,
Pedro