1. ## Determine a Set

Im taking a mathematical proofs class and im thrown off on what the X's mean in this problem ! Any Advice?

Let U={1,2,3,4} be the universal set, and let A={1,2,3}. Determine the set S={X e P(A) : lXl =the complement of lXl} by listing its elements

2. Originally Posted by nikie1o2
Im taking a mathematical proofs class and im thrown off on what the X's mean in this problem ! Any Advice?

Let U={1,2,3,4} be the universal set, and let A={1,2,3}. Determine the set S={X e P(A) : lXl =the complement of lXl} by listing its elements
Please rewrite the question? As it is now, it is impossible to understand.
No set is equal to its complement. Usually |X| stands for the number of elements in the set X. Look up that notation in your text. What does it mean?

3. I can't type out the proper terminolgy used in my problem...its asking to determine a Set where X is a element of the power set of A, such that the cardinality of X equals the cardinality of the complement of X

4. Because the universe has four elements, then you want to list the subsets of A that have two elements.