Lemma 10.103.5. Let R be a Noetherian local ring with maximal ideal \mathfrak m. Let M be a finite R-module. Let x \in \mathfrak m be a nonzerodivisor on M. Then M is Cohen-Macaulay if and only if M/xM is Cohen-Macaulay.
Proof. By Lemma 10.72.7 we have \text{depth}(M/xM) = \text{depth}(M)-1. By Lemma 10.63.10 we have \dim (\text{Supp}(M/xM)) = \dim (\text{Supp}(M)) - 1. \square
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