Proving the Direct Sum Decomposition of a Vector Space

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Homework Help Overview

The discussion revolves around proving the direct sum decomposition of a vector space, specifically showing that a vector space V can be expressed as the direct sum of two subspaces U and W derived from a basis B.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the necessity of proving that elements in U and W are distinct and question the implications of assuming a nonzero vector exists in their intersection.

Discussion Status

Some participants have provided guidance on the assumptions involved in the proof, while others are questioning the need to demonstrate certain assumptions, indicating a mix of understanding and confusion regarding the proof's requirements.

Contextual Notes

There is a focus on the definitions of the subspaces and the implications of their intersection, with some participants expressing uncertainty about the assumptions made in the problem statement.

ashina14
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Homework Statement



Suppose B = {u1, u2.. un} is a basis of V. Let U = {u1, u2...ui} and W = {ui+1, ui+2... un}. Prove that V = U ⊕ W.

Homework Equations





The Attempt at a Solution



I think I should prove that elements in U are not in W and viceversa. Then this prove it is indeed a disjunction?
 
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Prove that if v is a nonzero vector in the intersection of U and W, then the u'is must be dependent.
 
How can I show v is non zero?
 
ashina14 said:
How can I show v is non zero?
You assume that v is nonzero - that's what "if v is nonzero" means. You don't need to show the things that you are assuming.
 
Thanks for the help guys :)
 

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