How to show U and W direct sum of V?

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Homework Help Overview

The discussion revolves around demonstrating that the vector space V = R^3 is the direct sum of the subspaces U and W, where W is generated by the vector w = (1, 0, 0) and U is generated by the vectors u_1 = (1, 1, 0) and u_2 = (0, 1, 1).

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the need to express each vector in V as a unique sum of vectors from U and W. There is a focus on showing the linear independence of the generating vectors and the uniqueness of the decomposition.

Discussion Status

Some participants have provided guidance on the necessity of demonstrating linear independence to establish uniqueness in the decomposition of vectors. There is an acknowledgment of the need to explore the intersection of U and W and confirm it contains only the zero vector.

Contextual Notes

Participants note the importance of adhering to forum guidelines, emphasizing the need for attempts or expressions of confusion rather than simply posting questions. There is an indication that the original poster is new to the forum and is seeking clarification on the problem-solving process.

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Let V = R^3. Let W be the space generated by w = (1, 0, 0), and let U be the subspace generated by u_1 = (1, 1, 0) and u_2 = (0, 1, 1). Show that V is the direct sum of W and U.
 
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Try and follow the forum guidelines, ok? Show an attempt or state what's confusing you. Don't just post the question. You want to show each vector in V=R^3 can be expressed as the sum of a vector in U and a vector in W in a unique way. Try it.
 
Last edited:
Dick said:
Try and follow the forum guidelines, ok? Show an attempt or state what's confusing you. Don't just post the question. You want to show each vector in V=R^3 can be expressed as the sum of a vector in U and a vector in W in a unique way. Try it.

Yes, I will. I'm sorry about the misunderstanding, I'm new to this forum.

First I let v = (2, 2, 1) E in R^3. Then I showed that v = u1 + u2 + w = (1 1 0) + (0 1 1) + (1 0 0) = (2 2 1) which still E in R^3. Now, how do I show that the intersection of U and W contains only 0. Do I do this by showing u1, u2, and w are linearly independent?
 
Well, you've only shown that one particular vector can be expressed as a sum, but you have show that way of decomposing v is unique. But, yes, if you show u1, u2 and w are linearly independent than you know that the coefficients are unique, and since there are 3 vectors, they span all of R^3.
 

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