1. The problem statement, all variables and given/known data V1 is defined as the span of the vectors b1,b2,b3,b4 Prove that V1 is not a vector space. 2. Relevant equations A set of axioms : If u and v are tow vectors in the span of b1,b2,b3,b4 then: 1. u + v belongs to V1 2. ku also belongs to V1 3. The attempt at a solution Don't know how to prove 1. wrong !