Question

Let V be the vector space of 2× 2 matrices over R. Check whether the subsets
W1 = { (a,1) ,(0,-a) | a ∈ R} and W2 = { (a,-a), (0,b)| a,b∈ R}
are subspaces over R. For those sets which are subspaces, find their dimension and a
basis over R.