find the determinant
0 1 -2
-2 2 0
-3 4 1
find the inverse
4 -5
1 -1
find the deterinant
-4 3
5 0
I expanded across the first row.
You should be able to do this one by using 1 and 3 as an outline.
Definition:
The determinant of an n x n matrix A is defined as
where
are the cofactors associated with the first row expansion.