thank you HallsofIvy you were right. I read wrong the question. it is if it is a subspace of the M(2,2), the vector space of all 2 by 2 matricess.
How to i proof that they are close under adittion and multiplication and if i consider the set B = |B1 B2|
B1 = 0 -6
-2 0
B2 = 2 4...