00:01
All right, so for this problem, we're given three equations.
00:03
That is x1 plus 3x2 minus 5 x3 equals 0.
00:18
The second equation is x1 plus 4x2 minus 8 x3 equals 0.
00:29
And the third equation is negative 3 x1 minus 7 x2.
00:37
Plus 9, x3, which is 0.
00:48
Sorry, it should be x3.
00:50
I'll write it down clearly and 0.
00:54
All right.
00:55
So we write it down in form of a matrix.
00:58
That is 1, 3, negative 5, 1, 4, negative 8, and negative 3, negative 7, and 9.
01:11
Now we're going to use the gaussian elimination.
01:15
So we first use the second row minus the first row.
01:19
So the first entry will be 0, second entry will be 1, and negative 8 minus negative 5.
01:26
That is 5 minus 8, so it's negative 3.
01:32
Negative 5.
01:35
All right, so for the third rule, we can add the first row times 3.
01:40
So that's negative 3 plus 3 times 3.
01:45
Times 1, so that is 0.
01:47
And negative 7 plus 3 times 3, that is 9.
01:51
So it's 9 minus 7, it's 2...