1. ## [SOLVED] Matrices

by using the cofactor expansion method i got det(A) = 14.

If i change that matrix using row operations into a upper triangular matrix..am i suppose to get the same determinant??? because i detrminant after row operations to be 5.

2. Originally Posted by b00yeah05

by using the cofactor expansion method i got det(A) = 14.

If i change that matrix using row operations into a upper triangular matrix..am i suppose to get the same determinant??? because i got 2.
There may be change to the determinant for each row op used, depending on the row operation:

You should know that:

1. Multiplication of a row by a constant multiplies the determinant by that constant.

2. Switching two rows changes the sign of the determinant.

3. Replacing one row by that row + a times another row has no effect on the determinant.

So you need to look at the row ops you did and make the appropriate changes to the determinant.