00:01
Recall that our stand -dus basis vectors are e1, e2, and e3.
00:05
So in this problem, we want to see which of these vectors can be added to a set of vectors to show that this new set is a basis.
00:12
Now, since all of these vectors are of length 3 and we're in r3, theorem 4 .5 .4 tells us that we just need to check that the set is linearly independent.
00:23
So let's look at our first two vectors, and i put those vectors into a matrix.
00:29
Now we see if we add these two vectors together, we just get e3.
00:34
So we know our answer e3 is not linearly independent of these two.
00:39
So let's go ahead and see if e2 is linearly independent.
00:44
So we put e2 into the last column of our matrix, and then we're going to try to reduce to row echelon form.
00:52
So first we'll use the first row to cancel out the second row, and we'll do that by multiplying the first row by two and adding it to the second.
01:02
So that gives a 0, a 0, and a 1.
01:07
And then to cancel out the 3 in our third row, we're going to multiply the top row by 3, and we will add it to the third row.
01:15
So that gives us a 0, that gives us a 1, and that gives us a 0.
01:22
So now we can use the bottom row to cancel out the 1 in the second entry of the top row, giving us the following.
01:34
And all i'm doing here is just taking negative of the last row and adding it to the first row.
01:50
And now we can see that each row in each column only has one entry, which implies these three vectors are linearly independent.
01:58
So the answer to part one is e2.
02:01
Now let's go ahead and put the vectors from part two into a matrix...