## Romero 3 years ago I remember reading that if you have a set of vectors that if one of the vectors is a lin combination of the vectors before it then the set is lin dependent. What I'm confused about is does that vector have to be lin combination of ALL of the previous vectors or just at least one for the set to be lin dependent?

1. Zarkon

a combination of one or more though if you can write it is a l.c. of one of the vectors you can write it is a linear combination of all the vectors

2. glgan1

I think should be all the combinations.

3. Romero

Great so if you want to get the basis of the set of vectors you get rid of the linear combination right?

4. Zarkon

you get rid off was many vectors as needed to make them independent (but no more)

5. Zarkon

*of

6. Romero

Ok let's say we have a a set of 3 vectors. We can't determine if it's lin dependent by inspection yet when we reduce it to echelon form we find a free variable so we only have two pivot points but this was done through row reduction using all the rows meaning we added or subtracted row 1 to row 2 and then used row 2 to make the third row a zero row. At that point if we want to have the basis of the set we have to get rid of a vector. Can we get rid of any vector?

7. Romero

Can we get rid of any vector? @Zarkon This is basically what I'm asking :)

8. Zarkon

yes

9. Romero

That's weird. So you can have three different basis for the set of vectors?

10. Romero

Does this mean that basis is not unique?

11. Zarkon

correct the basis is not unique...there can be an infinite number of basis's

12. Romero

Is there a condition where a basis will be unique?

13. Zarkon

|dw:1336751060283:dw||dw:1336751083709:dw| both a basis for \(\mathbb{R}^2\)

14. Zarkon

you would have to be pretty restrictive

15. Romero

What a bais for a vector space? Can that be infinite as well?

16. Zarkon

yes

17. Romero

and you can do this by multiplying the basis by a scalar?

18. Romero

to get infinite basis?

19. Zarkon

it is really too complicated to talk about here. I'd recommended you read http://en.wikipedia.org/wiki/Banach_space