Solution might be wrong

I don't think the solution is right - the vector <1 0 -1 0> is not orthogonal to the vectors spanned by W. If you let c and d be free variables, you get the vector <-1,-1,1,0> instead.

Good catch, are you happier with the new solution? The vector you found was correct.

In general, solutions that are listed as being "in progress" have not fully been reviewed and may contain more errors than completed solutions. Thanks for bringing this particular error to our attention.