00:01
This problem we're given, a is the matrix 4, negative 2, negative 2, 1, and b is the matrix given by 2 -1 -4 -2.
00:14
Now, we would like to find the product of the two matrices ab, and then we would also want to find the value of b.
00:21
Now, starting here with ab, this is equal to 4 -2 -negative 2 -1 times 2 -1 -4.
00:37
Now, to multiply matrices, we multiply rows by columns.
00:42
So we're going to take the rows of the first one times columns of the second.
00:47
Now, in doing this, we take 4 times 2 plus negative 2 times 4.
00:56
And that gives us 0.
00:57
And so here in the top left, we have 0.
01:02
Now moving over, first row times the second column.
01:06
This is 4 times 1 plus negative 2 times 2.
01:12
And again, that goes to zero.
01:18
Moving down, second row times first column, negative 2 times 2 plus 1 times 4 gives us 0 again.
01:31
And then lastly, that last row times the last column is native 2 times 1 plus 1 times 2.
01:38
And that again gives us 0...