Really basic linear algebra: subspaces of F[a,b]

In summary, the conversation is about determining which sets of functions are subsets of a given set F[a,b]. The functions in question have different properties, such as f(a) = 0 or f(a) = 1, and the individual talking is struggling to understand what is being asked of them. They ask for clarification on what F[a,b] represents and what it means to be a subset or subspace of it. The conversation ends with a suggestion to think about the closed under addition and multiplication properties in order to determine which set of functions satisfies them.
  • #1
slugbunny
15
0

Homework Statement



Determine which of the following sets of functions are subsets of F[a,b]

a) All functions f in F[a,b] for which f(a) = 0
b) All functions f in F[a,b] for which f(a) = 1


The Attempt at a Solution



Ok so I am just learning about vector subspaces. After reading the text multiple times, I am still at a lost. Can someone please explain to me in plain English what these evil math people want from me?

Thanks guys for your much appreciated help :smile:
 
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  • #2
What's F[a,b] defined as? I assume it's some set of functions defined on the interval [a,b], but what particular properties must these functions have?
 
  • #3
Thanks for your reply! Unfortunately F wasn't given any particular properties
 
  • #4
What is F[a,b] defined as?


P.S. did you mean "subset of F[a,b]" or did you mean "subspace of F[a,b]"?
 
  • #5
oops sorry about that, I meant "subspace of F[a,b]"

F is the matrix with vectors a and b? :|
 
  • #6
slugbunny said:
F is the matrix with vectors a and b? :|
That doesn't make any sense. Instead of guessing, please tell us what F[a, b] means relative to this problem. It should say in the problem itself.
 
  • #7
OK, the first thing you need to do is go figure out what the notation "F[a,b]" means. Don't just make wild guesses. It should be explained in your textbook or notes somewhere.
 
  • #8
You have to think about the basic closed under addition and closed under multiplication properties, to see if a) or b) satisfy them.
For example, would adding f(a)=0 and say g(a)=0 still be in this subspace?
What about for f(a)+g(a) = 1 + 1?
That should give you a clear hint.
 

1. What are subspaces in linear algebra?

In linear algebra, subspaces refer to a subset of a vector space that is closed under vector addition and scalar multiplication. This means that if you take any two vectors from the subspace and add them together, the resulting vector will still be in the subspace. Similarly, multiplying a vector in the subspace by a scalar will also result in a vector that is still within the subspace.

2. How do you determine if a set of vectors is a subspace?

In order for a set of vectors to be considered a subspace, it must meet three conditions: it must contain the zero vector, it must be closed under vector addition, and it must be closed under scalar multiplication. This means that if you take any two vectors in the set and add them together or multiply them by a scalar, the resulting vector must also be in the set.

3. Can you give an example of a subspace?

One example of a subspace is the set of all 2-dimensional vectors with real number components. This set contains the zero vector, is closed under vector addition (e.g. (1,2) + (3,4) = (4,6) which is still a 2-dimensional vector), and is closed under scalar multiplication (e.g. 2(1,2) = (2,4) which is still a 2-dimensional vector).

4. What is the difference between a subspace and a span?

A span is the set of all possible linear combinations of a given set of vectors. It can include vectors that are not necessarily in the original set. A subspace, on the other hand, must contain the original set of vectors and must also be closed under addition and scalar multiplication.

5. How are subspaces used in real-world applications?

Subspaces are used in a variety of real-world applications, including data analysis, computer graphics, and machine learning. In data analysis, subspaces are used to represent patterns and relationships within a dataset. In computer graphics, subspaces are used to create 3-dimensional images and animations. In machine learning, subspaces are used to reduce the dimensionality of data, making it easier to analyze and classify.

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