Using Sarru’s rule, we have Scheme 1, which will be formed from the description of two first
columns of the determinants (first and second columns). The terms, which will be formed by the
products of diagonal elements in the right side of scheme 1, become the “+“ sign (red) and the
left side in this scheme become the “-“ sign (blue). 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: