Properties of Determinants for Lower Triangular Matrices?

[cragar]

Homework Statement

I keep trying to turn a 4x4 matrix into a lower triangular matrix and then multiply along the diagonal to get the determinant , but I can't get the answer in the back of the book , is there some property about determinates I am missing .

 

[Mark44]

Hard to say without seeing your work.

BTW, the word is determinant.

 

[cragar]

ok as long as we add rows together it doesn't change the det(A)
i can go 5R1+R2=R2 and it won't change the det(A) correct.

 

[Mark44]

Right. Of the three row operations, the only ones that change the value of the determinant are replacing a row by a multiple of itself (R_n <-- k*R_n) and switching two rows (R_n <--> R_m).