Calculation of determinant on HP-15C

[C.Ret]

This is a normal and common fact on any calculators to get approximation on most arithmetic operations.

Fortunately, the HP-15C have a rounding function. Select the expected precision of your specific application by using the appropriate f FIX n command, compute your 4x4 matrix determinant and then evacuate discrepancies by pressing g RND.

You will see your 2.1 E-10 result being transform in a zero.

May I suggest you to give us a printout of your specific matrix. Perhaps, same expert of the forum may found a twisted way or a smart arrangement that make the computation straightforward !?

Here is an exemple of a matrix 4x4 composed of sixteen small integers whose determinant is -3276. Despite using a LU decomposition, the HP-15C give the correct and accurate integer value of the determinant.

\( \begin{bmatrix}4&7&7&8\\ 5&-1&2&-4\\ 3&12&-5&6\\ 1&4&7&2 \end{bmatrix}=-3276 \)