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Homework Help: Linear Span Subsets

  1. Nov 13, 2014 #1
    This question asks me to prove a statement regarding linear spans. I have devised a proof but I am not sure if it is substantial enough to prove the statement.

    1. The problem statement, all variables and given/known data

    Let L(S) be the subspace spanned by a subset S of a linear space V. Prove that if S is a subset of T and T is a subset of V and if T is a subspace of V, then L(S) is a subspace of T. (This property is described by saying that L(S) is the smallest subspace of V which contains S).

    2. Relevant equations
    In part (a) of the question I proved that for S={u1, ..., un}, S is always a subset of L(S).

    3. The attempt at a solution
    From the definition of the span of S, we know that L(S) is the smallest subspace of V that contains S. Therefore, for any T that is a subset of V such that S is a subset of T, it is clear from the definition of span that L(S) is a subset of T.
    Is this proof substantial enough?
  2. jcsd
  3. Nov 13, 2014 #2


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    Gold Member

    No. Because you don't use the fact that T is a subspace.
    You can use the fact that L(S) is the smallest subspace containing S or consider L(T).
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