Proving (u,v,u+v) Cannot Be a Basis for <u,v,u+v>

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In summary, by showing that (u,v,u+v) can be written as a linear combination of u, v, and (u+v) with non-zero coefficients, we have proven that they are linearly dependent and cannot form a basis for <u,v,u+v>.
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Homework Statement



Prove (u,v,u+v) can not be a basis for <u,v,u+v>.


Homework Equations





The Attempt at a Solution



Let αu+βv+γ(u+v)=0
αu+βv=-γ(u+v)
α/γ(u)+β/γ(v)=-(u+v)
α/γ(u)+β/γ(v)+1*(u+v)=0

Since α/γ,β/γ,1 are not all zeros, therefore, (u,v,u+v) are linearly dependent. Hence it doesn't form basis for <u,v,u+v>.


Let me know if this is the right approach towards the proof.
 
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  • #2
Showing that (u,v,u+v) are linearly dependent is the correct way to prove they don't form a basis. To show that they are linearly dependent, you only have to find an example of α, β, and γ (not all zero) for which αu+βv+γ(u+v)=0. I would just write down a specific choice of numbers that works; this is not difficult to do by guess and check.
 
  • #3
So I guess we can achieve that by saying the following:

-1*(u) + (-1)*v + 1*(u+v) = 0

Since none of the constants are actually zero. Therefore, (u,v,u+v) are infact linealy dependent.
 

1. What is the definition of a basis in mathematics?

A basis is a set of linearly independent vectors that span a vector space. In other words, every vector in the vector space can be written as a linear combination of the basis vectors.

2. Why is proving (u,v,u+v) cannot be a basis important?

Proving that a set of vectors cannot be a basis is important because it helps us understand the limitations and properties of vector spaces. It also allows us to identify when a set of vectors is not suitable for certain mathematical operations.

3. What does it mean for (u,v,u+v) to be linearly independent?

A set of vectors is linearly independent if none of the vectors in the set can be written as a linear combination of the other vectors. In other words, no vector in the set is redundant or can be removed without changing the span of the set.

4. How can we prove that (u,v,u+v) cannot be a basis?

We can prove that a set of vectors cannot be a basis by showing that the vectors are linearly dependent or by demonstrating that they do not span the vector space. In this case, we can show that the vector u+v can be written as a linear combination of u and v, making the set linearly dependent.

5. Are there any alternatives to proving (u,v,u+v) cannot be a basis?

Yes, there are alternative methods to prove that a set of vectors cannot be a basis. One method is to show that the vectors are not orthogonal, meaning they are not perpendicular to each other. Another method is to demonstrate that the vectors do not form a complete set, meaning they do not span the entire vector space.

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