Span is the set of all symmetric 2x2 matrices

Show that if

M1= (1 0), M2= (0 0) M3 = (0 1),
(0 0) (0 1) (1 0)

then the span of {M1, M2, M3} is the set of all symmetric 2 x 2 matrices.


I need to find the set of all linear combinations of the matrices. Can I have a hint for this problem?

P.S. I read up on fields from my previous question and it still doesn't make sense to me.

The matrix notation didn't come out good, The numbers in parentheses should be placed one directly over the other to indicate a matrix. Sorry.