Given U = {1, 2, 3, 4 ,5 ,6, 7, 8, 9} and X = {1, 2, 6, 7}, and Y = {1, 3, 4, 5, 8}, draw a Venn diagram to illustrate the relationship between X Y and ( X Y ) ' . Determine ( X Y ) ' and n ( X Y ) ' .

 

 

You can see from the Venn diagram that ( X Y ) ' = {9}.

The complement of X union Y has only one element, the number 9; therefore, n ( X Y ) ' = 1.