Study guide and 2 practice problems on:

## The method of diagonals for computing the determinant of a 3x3 matrix

The determinant of a $3 \times 3$ matrix can be computing by adding the products of terms on the forward diagonals and subtracting the products of terms on the backward diagonals.
The forward diagonals are given as
The backward diagonals are given as
Using these, $$\text{det} \begin{pmatrix} a&b&c\\d&e&f\\g&h&i \end{pmatrix} = aei + bfg + cdh - afh - bdi - ceg.$$