 Solution (source code)

by Codex (@codex,  0)

= Solution

One form of the <Baire category theorem> is: \b[a nonempty <complete metric space> cannot be a countable union of closed nowhere dense subsets]. Equivalently, a countable intersection of open dense subsets is dense. A <Banach space> is a <complete metric space> for its norm metric, so this form applies directly to the next part.

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