00:01
In this video we're going to solve this system of equations via gaussian elimination.
00:05
First we need to write this in the gaussian format by writing down a matrix of the coefficients of our variables and what they're equal to.
00:14
So for this we'll get 1 -1 -1 -1 -1 minus 2, 2 minus 1, 2 minus 1, 2, minus 1, 7, minus 1, 2, minus 1, 7, minus 1, 2, 2, 2, 2, 2, 2.
00:30
Minus 1 and now we're going to try and get as many zeros as we can so we can see these two can cancel and these two can cancel so we're going to take row 1 and replace it by row 1 plus row 2 similarly we can find a cancellation by looking at these ones here so if we replace row three by row three plus row one, we'll get more zeros as well.
01:14
So this brings us to 1 plus 2, 3, 1 minus 1, 0, minus 2, 1 ,000, 1 minus 1, 0, minus 7, 5.
01:25
Row 2 remains the same, 2 minus 1, 2 minus 1 7.
01:30
Row 3 minus 1 plus 1 0 2 plus 1 3 1 0 2 plus 1 3 minus 1 minus 2 minus 3 and then finally we can eliminate here by replacing row 2 by 3 times row 2 plus row 3 so the first row remains the same second row 3 3 3 3 three times it gives six, zero, six, i'll move this zero for more space.
02:13
Zero, then we have 21 minus three, which is 18.
02:21
And then the final row remains unchanged.
02:26
Now we're going to extract what information we can...