Autopia.org - View Single Post - Any Math Majors? Need discrete mathamatics help..

ifoam · 08-28-06, 02:10

If A = {1, 2, 3} and B = {4, 5}, then {<1, 4>, <2, 5>, <3, 5>}, for example, is a binary relation from A to B.
However, {<1, 1>, <1, 4>, <3, 5>} is not a binary relation from A to B because 1 is not in B.

I don't understand why the first part is true. Why are <1,5> <2,4> and <3,4> not included in the relation?

I DO understand the second part. Since a binary relation from a set A to a set B is a set of ordered pairs <a, b> where a is an element of A and b is an element of B.

Anyone have any insite?

08-28-06, 02:10	#1 (permalink)
ifoam Registered User ifoam is offline Join Date: Jun 2006 Location: Pharr, Texas Posts: 126	Any Math Majors? Need discrete mathamatics help.. If A = {1, 2, 3} and B = {4, 5}, then {<1, 4>, <2, 5>, <3, 5>}, for example, is a binary relation from A to B. However, {<1, 1>, <1, 4>, <3, 5>} is not a binary relation from A to B because 1 is not in B. I don't understand why the first part is true. Why are <1,5> <2,4> and <3,4> not included in the relation? I DO understand the second part. Since a binary relation from a set A to a set B is a set of ordered pairs <a, b> where a is an element of A and b is an element of B. Anyone have any insite?