00:01
Hello there, so here we got this matrix, is a 3x3 matrix, and we need to find the determinant.
00:07
In this case, we can choose any row or column that make easier the computations.
00:13
So whenever you want to compute the determinant of a matrix, you should choose the row or the column with the most zero.
00:21
So for example, in this exercise, you could choose either this row or this column, and that will make the computation really easy.
00:30
So here i'm going to choose the first column because i think that it's easier because it appears just the one as a coefficient and here appear the three.
00:41
So maybe we need to multiply and that will be an extra effort.
00:48
Okay, so i'm going to choose the first column.
00:53
So if i choose the first column, then the determinant of this matrix will be a11c11, 1.
01:03
Plus a to 1, c21, plus a31, c31.
01:10
But we know that a21 and a31 are 0.
01:16
So these components are equals to 0, and we just need to focus on these coefficients here.
01:23
So c11 refers to the co -factor, because here we are applying the expanding by cofactors method...