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Empty set relations/functions question

I just don't even know where to start. If someone could point me in the right direction / give me some guidance that would be great :smile:

[br]Whichofthefollowingrelationscanbefunctions?(justify)[br][br](a)Rf:∅↔∅[br][br](b)Rf:{∅}↔∅[br][br][br][br]Which of the following relations can be functions? (justify) [br][br](a) R_f : \emptyset \leftrightarrow \emptyset[br][br](b) R_f : \{\emptyset\} \leftrightarrow \emptyset[br][br][br]

Thanks!
(edited 9 years ago)
Original post by SummerPi
I just don't even know where to start. If someone could point me in the right direction / give me some guidance that would be great :smile:

[br]Whichofthefollowingrelationscanbefunctions?(justify)[br][br](a)Rf:∅↔∅[br][br](b)Rf:{∅}↔∅[br][br][br][br]Which of the following relations can be functions? (justify) [br][br](a) R_f : \emptyset \leftrightarrow \emptyset[br][br](b) R_f : \{\emptyset\} \leftrightarrow \emptyset[br][br][br]

Thanks!


Think about how you define a function:

Let X,YX, Y be sets a function from X to Y f:X→Y⊂X×Y:∀x∈X∃!y∈Y:y=f(x)f:X \rightarrow Y \subset X \times Y: \forall x \in X \exists! y\in Y : y=f(x)

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