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.