00:03
So here we are asked to find the determinant of the square matrix using expansion by cofactors.
00:09
Expansion by cofactors tells us that the determinant is a11 -c -1 -1 plus a -12, c -12, plus a -13, c -13.
00:25
So a -1 -1 is the element in row 1, column 1, which is simply the number 1.
00:34
Have the number one.
00:37
And c11 is basically minor m1, which means that we delete row one and column one.
00:47
So we're left with 5, negative 2, 3, negative 2.
00:54
A12 is the element in row 1, column 2, which is 3.
00:59
So we have three.
01:02
C1 .2 is the negative version of m1.
01:06
So let's find m12.
01:08
M12 is found by deleting row 1, and this time, column 2.
01:13
So we have negative 2, 3, and 3 negative 2.
01:19
A13 is the element in row 1, column 3, which is just 1.
01:27
And c13 is m13, which means that we just delete.
01:32
Row 1 and column 3.
01:34
So we're left with 2, 3, 5, negative 2...