Let W be a subspace of R^n and suppose that v1,v2,w1,w2,w3 are
vectors in W. Suppose that v1; v2 are linearly independent and that
w1;w2;w3 span W.
(a) If dimW = 3 prove that there is a vector in W that is not
equal to a linear combination of v1 and v2.
(b) If w3 is a linear combination of w1 and w2 prove that w1 and
w2 span W.
(c) If w3 is a linear combination of w1 and...