Equivalence Relation

Question

Consider the following relations:

$R_1: ((a, b), (c, d)) belongs to R $ iff a + d = b + c

$R_2: ((a, b), (c, d)) belongs R$ iff ad = bc

Which of the following is equivalence relation.

Comments

Your explanation is good enough.

But I generally do such questions by putting some random values.

Is that correct way to reach the answer as well?

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I generally do such questions by putting some random values.

yeah I also do the same way 

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@Magma @`JEET The value of x in the example should be ((a,b),(c,d)) as $R_{1}$ is $R\times R\rightarrow R\times R$ not $R\rightarrow R$.

Doesn't affect the answer but still !