1. The problem statement, all variables and given/known data Given matrix A (size m x n), prove N(A) is subset of N( A^t A). A^t is matrix A transposed. 2. Relevant equations 3. The attempt at a solution My assumption is m < n, using definition of nullspace, I ended up with N( A^t A) = a set of zero vector, while N(A) is not entirely included in N( A^t A). Thank You.