While the determinant of the third order expansion by the elements of whatever row
we have, see [4], [5], [6], [8]:
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:
Let’s start by describing before the first row element which lie in cutting the first row
with third column and before third row element which lie in cutting the third row
with third column ( 13 33 a and a ), as well in same manner let’s describe after first and
third row elements ( 11 31 a and a ), respectively. Now get such a scheme (Scheme 5.):