Lemma 10.32.3. Let R \to R' be a ring map and let I \subset R be a locally nilpotent ideal. Then IR' is a locally nilpotent ideal of R'.
Proof. This follows from the fact that if x, y \in R' are nilpotent, then x + y is nilpotent too. Namely, if x^ n = 0 and y^ m = 0, then (x + y)^{n + m - 1} = 0. \square
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