Determinants

The symbol is a determinant of third order that consists of nine numbers arranged in three rows and three columns.
By definition, the value of a determinant of third order is given by:

|A| = a₁₁a₂₂a₃₃+a₁₃a₂₁a₃₂+a₁₂a₂₃a₃₁-a₁₃a₂₂a₃₁-a₁₂a₂₁a₃₃-a₁₁a₂₃a₃₃

and is called the expansion of the determinant.

To remember easily, you can use:

Express the value of the determinant:

-2	5	5
2	-4	0
2	-3	-3