( ) , ( ) . , . , Y. . , - X.
, , = {2, 3} Y = {3, 4, 5, 6}. = {(2, 3), (2, 4), (2, 5), (2, 6), (3, 3), (3, 4), (3, 5), (3, 6)}. ³ = {(2, 4), (2, 6), (3, 3), (3, 6)}, = = {(3, 3)}, > Æ. .
X, , X. . , U P(U) .
X:
1) () , (, 볻 );
2) () , = (, );
3) , (, ). , - Æ .
. , , z - - X. : A ; : A ; : ; : =, : , yx ; : yz z.
, .