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קבוצה סגורה ברלציה

+1 vote
22 views
אם אומרים ש

{A,C}

קבוצה סגורה

האם זה אומר ש

A גורר את C

וגם

C גורר את A

או שאפשרי שרק אחד מהם מתקיים?
asked Feb 5, 2018 by tikitak (2,970 points)

1 Answer

+1 vote

If {A,B} is closed it only means that for every X not in {A,B}, It can't be that A -> X or B -> X (Or A,B -> X)

In your example, it can be that neither A -> C nor C ->A.

Notice, though, that if {A,C} is closed and it doesn't hold that A -> C, than {A} is also closed (and vice versa)

answered Feb 5, 2018 by Assaf (31,090 points)
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