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I am having problem in making relations for this question.

$S = \{1, 2, 3, 4\}, A = S \times S; (a,b) R (c,d)$ if and only if $ad = bc$.

I have made the following relations, but I am not sure if these are correct or not.

$R = \{(1,1), (2,2), (3,3), (4,4)\}$.

Please let me know what is the correct answer.


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Maybe I don't understand your notation, but $(a,b)R(c,d)$ is usually the same as saying $\bigl((a,b),(c,d)\bigr)\in R$, so I think $R$ should consist of ordered pairs of ordered pairs in the form $\bigl((x,y),(u,v)\bigr)$. – yunone Nov 28 '11 at 11:10
up vote 2 down vote accepted

A relation on a set $T$ is a set of ordered pairs of elements of $T$. Your $R$ is a relation on $A$, which is itself a set of ordered pairs, so $R$ is not a set of ordered pairs, but a set of ordered pairs of ordered pairs. It is the set of all things of the form $((a,b),(c,d))$ such that $ad=bc$. One element of $R$ is $((1,2),(2,4))$.

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Ok Thanks I got the point.. – Babu Nov 28 '11 at 11:53

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