Bourbaki

Exercise 5, § 5

Tag 03GQ, permanent. Cite it as [Bourbaki, Tag 03GQ].

Theory of Sets, I, 59

Let RR, SS, TT be relations in T\mathscr{T} and let xx be a letter. If RR is functional in xx in T\mathscr{T}, show that the following relations are theorems in T\mathscr{T} :

(not (∃x)(R and S))⇔(∃x)(R and (not S)),(\text{not } (\exists x)(R \text{ and } S)) \Leftrightarrow (\exists x)(R \text{ and } (\text{not } S)),
(∃x)(R and (S and T))⇔(∃x)(R and S) and (∃x)(R and T)),(\exists x)(R \text{ and } (S \text{ and } T)) \Leftrightarrow (\exists x)(R \text{ and } S) \text{ and } (\exists x)(R \text{ and } T)),
(∃x)(R and (S or T))⇔((∃x)(R and S) or (∃x)(R and T)).(\exists x)(R \text{ and } (S \text{ or } T)) \Leftrightarrow ((\exists x)(R \text{ and } S) \text{ or } (\exists x)(R \text{ and } T)).
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Transcribed from the printed volume. Not translated.