# Math Help - How to show, this is not vector space

1. ## How to show, this is not vector space

The set of all vectors $V = [v_1 , v_2 , v_3 , v_4]$ $R^4$ with $v_1+v_2=0$ and $v_3-v_4=1$ is not a vector space.
How can I begin this? I know all 9 properties of vector space, but how to show the proof.

2. How about the axiom that a vector space has an identity element of addition, zero vector?