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## Are any two infinite-dim. V.Spaces isomorphic?

 Quote by Landau and this is indeed "obviously" countable as Q,B and N are. To prove this, I would say given n, there are Q^n B^n linear combinations of n basis elements.
Q^nB^n is an upper bound at least, counting them in this way does not give an injection. But of course, as you know the space is at least countable, we are done.
 Recognitions: Science Advisor True. But you probably mean "at most countable" instead of "at least countable".

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