1. The problem statement, all variables and given/known data What choice of d would make matrix a b c d have a rank of 1? 2. Relevant equations rank(A) + nullity(A) = n 3. The attempt at a solution In order for rank = 1, then nullity must = 1 because n = 2. This isn't a nonsingular matrix, so det(A) = ad-bc =/= 0. d = bc/a, where 'a' cannot be 0. Let's say a = 1, then the matrix will be 1 ad/c c d c cannot be 0 either, so matrix is now 1 d 1 d and I guess a possible candidate would just then be 1 1 1 1? I think I'm supposed to give the answer in more arbitrary terms, so I am lost here.