00:01
So in this problem, we're given these sets and a vector space that these are in, and we're asked to determine if these sets are linearly independent.
00:20
So if they're linearly independent, then i cannot write one of them as a linear combination of the others in the set.
00:30
So in other words, if i set up a matrix of these vectors, these column vectors, and if i can row reduce it and get the identity matrix, for example, in this first one, the identity matrix, then they're all linearly independent.
00:48
If i get a row of zeros, they're not.
00:52
So let's set this up.
00:54
1 minus 1 2, 1, 1, 2, 1, 1, 4.
01:02
All right, so let's do row 2 minus row 1, and row 3.
01:10
See, that would be plus, minus 2 times row 1.
01:14
So row 1 stays the same, 1, 1, 1, 1.
01:18
A 0 here, 1 is minus 1 plus 1.
01:22
See, minus 2 plus 1, that would be minus 1, and 1 is 2.
01:29
And then the 0 here, and 1 minus 2, that's minus 1, and 4 minus 2 is 2.
01:41
And now we can see that we're going to have a problem, right? because row 3 is equal to row 2.
01:57
So with row 3 equal to row 2, let's do this.
02:02
Let's take row 3 minus row 2.
02:05
We get 1 -1 -1 -0 minus 1 -2, 0 -0, and now we are not literally independent.
02:37
In other words, we are linearly dependent on this one.
02:53
Okay.
02:55
Next one, we have these three vectors in r3 again.
02:59
So do the same thing.
03:00
Set this up.
03:01
1 minus 1, 2, 201, minus 1, 2 minus 1.
03:10
Okay.
03:11
Okay, so we take row 2 minus plus row 1, and row 3 minus 2 times row 1.
03:21
So i get 1, 2 minus 1.
03:24
I get 0, 0 plus 2 is 2, and 2 and minus 1 would be 1.
03:34
And then row 3, the 2, minus 2, again to the 0, and then 1 minus 4.
03:44
That's minus 3 and then minus 1 plus 2 because minus and minus is plus 2 is a 1.
03:57
Okay, so now let's take the negative of row 3 and subtract row 2 from it.
04:13
I'm trying to get a 1.
04:16
I'm trying to get a 1 here, right? let me do this.
04:30
Let's do this.
04:31
Let's take row 2 plus row 3 that will get give me a negative 1 here, and so then i'll take the negative of it.
04:47
So 1, 2, minus 1, 0, right? rowe 2 plus row 3 is negative 1.
04:55
Take a negative of that, gives me a positive 1.
04:57
1 and 1 is 2, so that's negative 2, 0, negative 3, 1.
05:06
Okay.
05:08
Now, let's take row 1 minus 2 times row 1, 0 ,000...