Set Theory Basics and Number Types
Sets are simply collections of objects written in curly brackets, like A = {2, 4, 6}. Think of them as mathematical containers that hold specific items called elements.
The mathematical world is built on different types of number sets. Natural numbers are your basic counting numbers (1, 2, 3...), which expand into integers when you add negative numbers. Rational numbers can be written as fractions, whilst irrational numbers like π can't be expressed as simple fractions.
Key notation you'll need includes: x ∈ A (x is in set A), x ∉ A (x is not in set A), and n(A) for counting elements. The empty set (∅) contains nothing, whilst the universal set (ξ) contains everything relevant to your problem.
Quick Tip: Think of the universal set as the "universe" your problem exists in - everything else is just a subset of this main collection.
