# How can I prove R[x] is integrally closed iff R is integrally closed ? (R: integral domain) [closed]

$R$ is a integral domain. How can I prove $R[x]$ is integrally closed iff $R$ is integrally closed?

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## closed as too localized by Qiaochu Yuan, Martin Brandenburg, Alon Amit, Robin Chapman, Gjergji ZaimiJul 25 '10 at 12:14

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Hi, this is Exer 4.18 of Eisenbud, there are plenty of hints in the Appendix. –  Hailong Dao Jul 25 '10 at 6:46
The way the question is phrased makes it sound like homework. What have you tried so far? Is one of the two directions easier than the other? –  Pete L. Clark Jul 25 '10 at 7:00