From the description of two first columns of the determinants (first and second
columns) will be formed Scheme 1. respectively two rows ( first and second rows)
will be formed Scheme 2.The terms, which will be formed by the products of
diagonal elements in the left side in both of scheme 1 and 2 become the “-“sign. In
this way we get the Sarrus’ rule, which are valuable just to compute the determinants
of the third order. In base of the Sarrus’s rule we have: