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Continuous functions and dense subset proof...?

Let f and g be continuous functions from a metric space X into a metric space Y. Let S be a dense subset of X. Prove that f(S) is dense in f(X).

How should I approach this? Thank you.

3 Answers

Relevance
  • 8 years ago
    Favorite Answer

    Hi A A,

    You have to show that i) every point in f(X) is either in f(S) or ii) is a limit point of f(S). In the following, assume that y is in f(X) and f(x) = y:

    i) If x is in S, the f(x) is in f(S)

    ii) Suppose x is a limit point of S. The idea is that since there is a sequence of points x_n in X that tend to x, the sequence of points f(x_n) tends to f(x) because of continuity.

    Hope that helps!

    Daniel

  • Anonymous
    5 years ago

    My expensive fellowd192e0c4ad64a9c35fe32972477e4cd8 typically an unlimited dimensional vector area does no longer have a organic topology on it. What topology are you pondering on C[d192e0c4ad64a9c35fe32972477e4cd8d192e0c4ad64a9c35fe32972477e4cd8d192e0c4ad64a9c35fe32972477e4cd8]? then again: what's the area between applications you're speaking about? :-(

  • Eugene
    Lv 7
    8 years ago

    Since S is dense in X, cl(S) = X, where cl() denotes closure. Since f is continuous, f(cl(S)) ⊂ cl(f(S)), i.e., f(X) ⊂ cl(f(S)). Hence f(S) is dense in f(X).

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