Let $f:\mathbb{R} \rightarrow \mathbb{R}$ and $ f(x + y) = f(x) + f(y)$.

How can I show that $f$ is continuous, when $f$ is continuous at $f(0)$?


marked as duplicate by levap, TomGrubb, Dominik, dxiv, user296113 Dec 18 '16 at 19:52

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