Using express as

+a_3(\;\ldots\+a_4(\;\ldots\+a_5(\;\ldots\" alt="a_2(\;\ldots\+a_3(\;\ldots\+a_4(\;\ldots\+a_5(\;\ldots\" />

Those four vectors span and it is easy to prove they are linearly independent.

W2 = {(a1, a2, a3, a4, a5) E F^5: a2 = a3 = a4 and a1 + a5 = 0}

Same method solving previously the system.

Fernando Revilla