00:01
Okay, so we have a matrix a, which has four rows, and we want to find the elementary matrix e, such that ea gives the matrix resulting from a.
00:11
After the given row operation is performed, then find e inverse and is determined, and give the elementary row operation corresponding to e inverse.
00:21
So the raw operation performed is switching row four and row two, so row four and row two switch.
00:30
So what we're going to do is just take the identity, 1 -0 -0 -0 -0 -0 -0 -0 -0 -0 -0 -0 -0 -0 -1 -0 -0 -0 -1.
00:41
And this is wrong.
00:44
1 -0 here, 0 -1.
00:47
And if we switch the fourth and second rows, this gives us the actual matrix e that we're looking for.
00:53
So e is going to be just the identity with the second and fourth row switched.
00:58
So 1 -0 -0.
01:01
0 -0 -0 -1 -0 -0 -1 -0 and 0 -1 -0.
01:12
So this is e, and then let's think about what e inverse is.
01:17
Well, all we have to do to get back to where we started is switch the second and fourth rows again.
01:22
So if we switch the second and fourth rows with e, and then we want to get back to where we started, we can switch the second and the fourth roads again...