# Subspace prove question

1. Mar 4, 2009

### transgalactic

V is a vector space on feild F and there is a series$$v=(v_1,v_2,v_3,v_4)$$
which is independent on V
W_1=sp(v1,v2)
W_2=sp(v2,v3)
of V
prove that
$$W_1\cap W_2=sp(v2)$$
its obvious v2 exists in both groups .
how am i supposed to prove it
??

2. Mar 4, 2009

### HallsofIvy

Staff Emeritus
Since
$W_1\cap W_2$ is a subspace of W1, and W1 has dimension 2, it has dimension 1 or 2. If it has dimension 2, the it is equal to W2. But W_1 contains v1 which is not in $W_1\cap W_2$ so it is not of dimension 2.