Let S and T be the subspaces of generated by the matrices and

respectively, where

and

Determine dim(s) and dim(T).

---------------------

Now, the problem I have with this is that, I know how to find a basis (and hence a dimension) for vector spaces over real-number fields (i.e. ), by stacking the spanning vectors and reducing the matrix to echelon form, etc. But here we have matrices. How can I stack them?