1. Feb 1, 2010

### tc_11

Hi,

I am new with linear algebra, and I'm having a hard time wrapping my mind around the 0 vector and the additive identity v + 0 = v, where 0 is the 0 vector.
If I had a 2x2 matrix, and v + w = C + (C^T)*D ... (where (C^T) is the transpose, v & w are vectors, and C & D are matrices)... would the additive identity hold? I feel like it wouldn't, because I don't see how it would be unique... but I think I may be wrong.. can someone please help?

2. Feb 2, 2010

### Lord Crc

I can't make sense of your expression, how does adding two vectors get you a 2x2 matrix? Are you confusing something here, or am I the confused one?

Anyway, if the additive identity does not hold, you're not dealing with a vector space and all bets are off (as far as linear algebra is concerned). One of the requirements of a vector space $$V$$ is that there exists an element $$\mathbf{0} \in V$$ such that $$\mathbf{v} + \mathbf{0} = \mathbf{v}$$ for all $$\mathbf{v} \in V$$.

3. Feb 2, 2010

### tc_11

That's what I'm trying to prove though, that the additive identity v + 0 = v does in fact hold, and if not it's not a vector space, but we have to test the axioms anyway to see which ones do hold.
Addition of 2 vectors in this problem translates to:
vector v := C (where C is a 2x2 matrix)
vector w:= D (where D is a 2x2 matix)
(v+w):= C + (C^T)D
so i would set up my equation as v + 0 =? v
C + (C^T)D =? C

4. Feb 2, 2010