Review of some stuff u may hv forgotten (omitted commonly known things)
- A set is: closed
- set of ints Z closed under addition but no under division b/c all added numbers result in a int
- Relation over a domain D
- Set union = merge
- intersection = all in common elements
- Complement A’ = all elements not in A that are in some universal set
- relation: set of ordered pairs where one element may be shared in multiple pairs
- reflexive: each pair can be swapped