A 3x3 triangular (or one non-zero each row), all positive => det(A)>=0? negative?
A 3x3, all coeff mult of 5, det(A) mult of ?
3x3, row 1 mult of 2, row 2 mult of 3, col 3 mult of 4. det(A) mult of ?
Given det and some coeff, find other coeffs.

