Practice!

Sample Problem

Find the determinant of

det(A)=

Solution

The determinant of A is the sum of the entries in ANY row or column of A multiplied by their respective cofactors. In this case, let’s choose column 4 because there are three zero entries in the first, second, and third rows of the fourth column.

The determinant of

Since a14, a24, and a34 are all equal to 0 à |A|=a44C44

C44=(-1)4+4M44=1*2=2

|A|=a44C44=2*2=4