Expanding by Minors: Understanding the Process of Computing Determinants

[brad sue]

Hi guys, what doe it mean when we are asked to compute the determinant the following way:

compute determinant across first row, down second column:
|1_0_3|
|2_2_1|
|4_0_3|

I know how to compute but here I need to understand the way to do it.

Thank you
B

 

[Galileo]

They are likely asking you to compute the determinant in two ways:
(1) Across the first row
(2) Down the second column
As you know, you can expand the determinant across any row or column.

 

[HallsofIvy]

It's talking about "expanding by minors". Do you know how to do that?