### using cofactor method find the determinant

Posted:

**Thu 19 May, 2011 16:08**find the determinant of

how can should I proceed?

Solution:

choose a column with most zeros. I'll choose column 1 with the values:

`[[0],[0],[3],[0]]`

from this column we can use only 3 because the other values are 0. 3 is located at row 3 column 1 `(-1)^(r+c)=(-1)^(1+3)=+1` so the sign for 3 is +.

Now using the first column with 3, we assume column 1 and row 3 (row 3 which has the 3 in it) does not exist and write our matrix:

`| [8, 0, 1],[ 7, 3, -1],[ 0, 0, 2],[ -5, 0, 6]|`

- Code: Select all
`B =`

0 8 0 1

0 7 3 -1

3 0 0 2

0 -5 0 6

how can should I proceed?

Solution:

choose a column with most zeros. I'll choose column 1 with the values:

`[[0],[0],[3],[0]]`

from this column we can use only 3 because the other values are 0. 3 is located at row 3 column 1 `(-1)^(r+c)=(-1)^(1+3)=+1` so the sign for 3 is +.

Now using the first column with 3, we assume column 1 and row 3 (row 3 which has the 3 in it) does not exist and write our matrix:

`| [8, 0, 1],[ 7, 3, -1],[ 0, 0, 2],[ -5, 0, 6]|`