00:01
To find the subspace, or the basis that is the basis of the subspace spanned by v1, v2, v3, and b4, we need to find the column space of the matrix made of the columns v1 v2, v4.
00:14
So we make this matrix, and we do gaussian elimination to find the column space.
00:18
So our first row stays the same, and we see our second row can be scaled down by a factor of 3, so we get 0 -1 -1.
00:28
1.
00:30
Then we see we take our first row and subtract it from our third row, which gives us 0, 10, 10, and 10.
00:41
And then we take our first row and subtract it from our last row, giving us 0, 4, 4, and 4.
00:54
Well, at this point, we see that the third and the fourth row are just scalar multiples of the second row.
01:02
So that means that we can cancel out those rows completely.
01:06
And then to get rid of this negative 3 in the top row, we're going to take three times the second row and add it to the top row.
01:14
So that's going to give us a 1, a 0, a 2, and then negative 3, excuse me, a negative 2.
01:30
And then we have 0s everywhere else...