1. The problem statement, all variables and given/known data I've attached the problem, it involves reducing a 3x3 matrix determinant to row echelon form, but the leading diagonal elements have to be linear in a and b afterwards. 2. Relevant equations 3. The attempt at a solution I've managed to convert it to row echelon form by: r3-ar2 ; r2-ar1 ; r3-br2 The problem is that this leaves a diagonal element having cubic terms. Can anyone see a way to acomplish this? Should be an easy problem, but I've spent over an hour trying different combinations.