Hi, I have a question about span of vectors. The question is:

Find a basis of the subspace of R4 spanned by the following vectors:

[-4,1,6,-9],[1,-3,4,5],[3,2,-10,4],[5,-4,-2,14]

So I found the reduced row echelon form of these values stuck in an augmented matrix set equal to the zero vector and came up with

[[1,0,-1,-1],[0,1,-1,1],[0,0,0,0],[0,0,0,0]]

And I assumed that [[1,0,-1,-1]] and [[0,1,-1,1]] would be the answers but this was incorrect. Is anyone able to give any insight as to where I have gone wrong? Thanks for any help in advance!