00:01
To solve this system, we actually have four variables here.
00:03
X, we have y, we have z, and we have w.
00:09
When i'm making this matrix, i'm going to make sure that the column with x has all our x variables, and so on and so forth.
00:21
So our first equation is x plus z plus w equals 4.
00:25
X plus 0y z plus w next equation is y minus z equals negative 4 y minus z equals negative 4 next equation is x minus 2y minus 2y plus 3 z plus w equals 12 and finally we have 2x minus 2 z plus 2 z plus w equals 12 and finally we have 2x minus 2 z plus 5w equals negative 1.
01:18
Here we can do some row reductions to actually simplify this matrix.
01:25
We already have a 1 here and a 0 here.
01:28
So now we have to get zeros here and here.
01:31
So to do that, we take this third row and subtract the first row.
01:35
1 minus 1 is 0, negative 2 minus 0.
01:39
3 minus 1 is 2.
01:40
1 is 2.
01:41
1 minus 0.
01:43
12 minus 4 is 8.
01:45
We can take row 4, subtract 2 times row 1, 2 minus 2, 0 minus 0, 0, negative 2 minus 2 times 1 is negative 4, 5 minus 2 times 1 is 3, negative 1 minus 8 is negative 9.
02:05
Now what we have to do is we have to get a 0 in this position right here.
02:12
And you can do that a number of different ways.
02:14
The easiest for me would be to take row 3 and add 2.
02:18
Times row 2.
02:21
So we have negative 2 plus 2 times 1.
02:24
That's 0.
02:25
We have 2 plus 2 times negative 1.
02:29
It's also 0.
02:31
0 here.
02:32
And then we have 8 plus 2 times negative 4...