# discrete math relations simple problem help !!!!

• Dec 2nd 2012, 08:14 AM
ujnikm
discrete math relations simple problem help !!!!
Let A = {(x, y) | x, y integers}. Define a relation R on A by the rule (a, b) R (c, d) ↔ a = c or b = d. Determine whether R is transitive.
I know that it's not transitive but how to prove that is my problem.
shall I prove it with an example with numbers or with letters???!!!
• Dec 2nd 2012, 08:34 AM
Plato
Re: discrete math relations simple problem help !!!!
Quote:

Originally Posted by ujnikm
Let A = {(x, y) | x, y integers}. Define a relation R on A by the rule (a, b) R (c, d) ↔ a = c or b = d. Determine whether R is transitive.
I know that it's not transitive but how to prove that is my problem.
shall I prove it with an example with numbers or with letters???!!!

You give a counterexample. But it must be done with integers.

\$\displaystyle (1,3)R(1,2)~\&~(1,2)R(4,2)\$ BUT ?
• Dec 2nd 2012, 11:20 AM
ujnikm
Re: discrete math relations simple problem help !!!!
Quote:

Originally Posted by Plato
You give a counterexample. But it must be done with integers.

\$\displaystyle (1,3)R(1,2)~\&~(1,2)R(4,2)\$ BUT ?

can u illustrate more ??? please
• Dec 2nd 2012, 11:39 AM
Plato
Re: discrete math relations simple problem help !!!!
Quote:

Originally Posted by ujnikm
can u illustrate more ??? please

What do you mean. It is clear.

\$\displaystyle (1,3)R(1,2)~\&~(1,2)R(4,2)\$ BUT NOT \$\displaystyle (1,3)R(4,2)\$