"Span of a Subspace - Does it Equal x?

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In summary, the conversation discusses the relationship between a subspace x and its span. It is stated that for any "a" and "b" in x, their sum and scalar multiples also belong to x. However, the last statement is clarified to refer to vectors in x, not x itself. It is also mentioned that one direction of the proof has been established, but the other direction still needs to be proven.
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safi
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Homework Statement



If x is a subspace of V so, span(x)=x

Homework Equations



span(x)=x


The Attempt at a Solution



If x is a subspace so, for any "a", "b" in x:
a+b∈x
and (c1)*a∈x

So a linear combination of x belongs to x but is equal to x?
 
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  • #2
Your last sentence is badly worded. There is no such thing as "a linear combination of x". You mean "a linear combination of vectors in x".

What you have proved is only one direction- you have proved that the span of x is a subset of x. Now you need to prove that x is a subset of span of x. That is easy. Suppose a is vector in x. Then 1a is in the span of x.
 
  • #3
Hi, thanks!
 
Last edited:

1. What is the definition of the span of a subspace?

The span of a subspace is the set of all possible linear combinations of its vectors. It represents the entire space that can be formed using those vectors.

2. How is the span of a subspace calculated?

The span of a subspace can be calculated by determining the linear independence of its vectors. If the vectors are linearly independent, then the span is equal to the number of vectors. If the vectors are linearly dependent, then the span is equal to the number of linearly independent vectors.

3. Does the span of a subspace always equal the number of vectors in the subspace?

No, the span of a subspace can be less than or equal to the number of vectors in the subspace. This depends on the linear independence of the vectors in the subspace.

4. Can the span of a subspace change?

Yes, the span of a subspace can change if the vectors in the subspace are changed or if new vectors are added to the subspace. However, the span will always be a subset of the original subspace.

5. How is the span of a subspace related to the dimension of a vector space?

The span of a subspace is directly related to the dimension of a vector space. The dimension of a vector space is equal to the maximum number of linearly independent vectors that can be formed from the subspace, which is equal to the span of the subspace.

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