Hey! I am studying for my linear algebra exam and am having some trouble with determining the determinant of a square matrix using cofactor expansion.
Here is an example of what I am having trouble with:
Question Attempted solution
I know that the determinant of this matrix is 5, I just can't seem to get that answer in what I am doing. I will use the first row in this attempt:

then replacing those 2x2 matrices with their determinants gives:
Which is NOT 5. I tried this with other columns and rows and am getting different answers for those. Am I doing this wrong or does it not work on some matrices???
Hopefully someone can help! Thanks for looking