00:01
On this question, we want to determine whether this pair of matrices are inverses or not.
00:06
So if they are inverses, then when we multiply them together, we should get the identity matrix, which looks like this.
00:16
So this is what we want to get when we multiply them together.
00:20
And if we do, then they're inverses.
00:22
So the best way to multiply matrices is if you take your first one, and then you write the second one above and to the right of it.
00:39
Then from here, what happens is that your answer is going to show up in this space right here.
00:49
So what you want to do is create a little grid.
00:51
So you're going to draw straight down between the columns and the matrix on top and between the rows over here.
00:58
So then it's easier to see where your numbers are coming from.
01:01
So this number right here is going to come from this column.
01:04
And this row.
01:07
So what you do is you multiply the first and the first, second and the second, and add them.
01:14
So in other words, that would be two times one -half plus zero times negative one.
01:22
So two times one -half is one, and then we get zero.
01:25
So that first element will be one...