The linear combinations of v=(a,b) and w=(c,d) fill the plane unless _____. Find four vectors u, v, w, z with four components each so that their combinations cu+dv+ew+fz produce all vectors (b1, b2, b3, b4) in four dimensional space. I think that the first part of the answer, that fills the blank, is unless v is a scalar multiple of w, or vice versa. But as far as the second part of the question, I have no idea what it is even asking. Are b1, etc. referencing the first part of the question? Or is it just asking to write vectors that have all zero components except b1 etc. Any help is much appreciated?