Vector Subspaces: Determining U as a Subspace of M4x4 Matrices

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SUMMARY

The discussion focuses on determining whether the subset U of all 4x4 upper symmetric matrices is a subspace of the vector space V of all M4x4 matrices. Participants emphasize the importance of demonstrating operational closure under addition and scalar multiplication to validate U as a subspace. The concept of upper symmetric matrices is clarified, with suggestions for the original poster (OP) to explore properties of vector spaces and provide counterexamples if necessary. The conversation highlights the need for a systematic approach to proving or disproving the subspace criteria.

PREREQUISITES
  • Understanding of vector space properties, including closure under addition and scalar multiplication.
  • Familiarity with matrix types, specifically upper symmetric matrices and their definitions.
  • Knowledge of linear algebra concepts, particularly subspaces and their characteristics.
  • Ability to construct counterexamples in mathematical proofs.
NEXT STEPS
  • Research the definition and properties of upper symmetric matrices in linear algebra.
  • Study the criteria for a subset to be considered a subspace of a vector space.
  • Learn how to construct counterexamples to demonstrate non-subspace properties.
  • Explore operational closure in vector spaces with practical examples.
USEFUL FOR

Students of linear algebra, mathematicians, and educators seeking to deepen their understanding of vector spaces and subspace properties, particularly in the context of matrix theory.

mathiebug7
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Determine whether the following subsets U of M4x4is a subspace of the vector space V of all M4x4 matrices, with
the standard operations of matrix addition and scalar multiplication. If is not a subspace provide an example to
demonstrate a property that U does not possess.
a. The set U of all 4x4 upper symmetric matrices
 
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What are upper symmetric matrices? Doesn't sound symmetric though. And what do you think? You should show us your work!
 
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mathiebug7 said:
a. The set U of all 4x4 upper symmetric matrices
I am familiar with "upper triangular" and "symmetric", but I don't know what "upper symmetric" is.

In any case, you should proceed step-by-step through the definition of a vector space and show whether or not each requirement is satisfied. If any of them are difficult, we can give hints and guidance on textbook-type problems where you show your work.
 
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fresh_42 said:
What are upper symmetric matrices? Doesn't sound symmetric though. And what do you think?
I'm guessing diagonal matrices. :wink:
 
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vela said:
I'm guessing diagonal matrices. :wink:
This could be a way out if there wasn't that "U" and the extensive description of how to find a counterexample. Very suspicious, Watson!
 
fresh_42 said:
This could be a way out if there wasn't that "U" and the extensive description of how to find a counterexample. Very suspicious, Watson!
The OP seems to have posed only the (a) part of the question. Presumably the b, c, etc parts have been left out …
 
vela said:
I'm guessing diagonal matrices. :wink:
That certainly would work. This gets my vote.
 
Ultimately, OP needs to show operational closure under addition, scaling.
 
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WWGD said:
Ultimately, OP needs to show operational closure under addition, scaling.
Good point. IMO, for a beginning student, it would be good for him to go down the properties and list the ones that are inherited. Then prove the closure properties that are not just inherited.
 
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