Lemma 47.3.3. Let R \to S be an epimorphism of rings. Let E be an S-module. If E is injective as an R-module, then E is an injective S-module.
Proof. This is true because \mathop{\mathrm{Hom}}\nolimits _ R(N, E) = \mathop{\mathrm{Hom}}\nolimits _ S(N, E) for any S-module N, see Algebra, Lemma 10.107.14. \square
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