Every bounded linear functional on a linear subspace of a real normed space extends to the whole space without increasing its norm.
The Hahn-Banach theorem is a fundamental result in functional analysis, particularly in the study of linear functionals on normed vector spaces. It has several formulations and applications, but its primary statement concerns the extension of linear functionals. ### Statement of the Hahn-Banach Theorem Informally, the theorem asserts that under certain conditions, a bounded linear functional defined on a subspace of a normed vector space can be extended to the whole space without increasing its norm.
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