2: Groups

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2.1: Binary Operations and Structures
So far we have been discussing sets. These are extremely simple objects, essentially mathematical “bags of stuff.” Without any added structure, their usefulness is very limited. A set with no added structure will not help us, say, solve a linear equation. What will help us with such things are objects such as groups, rings, fields, and vector spaces. These are sets equipped with binary operations which allow us to combine set elements in various ways.
2.2: Exercises, Part I
This page contains part I of the exercises for Chapter 2.
2.3: The Definition of a Group
In summary, we used associativity, identity elements, and inverses in a set of all integers to solve the given equation. This perhaps suggests that these would be useful traits for a binary structure and/or its operation to have. They are in fact so useful that a binary structure displaying these characteristics is given a special name. We note that these axioms are rather strong; “most” binary structures aren't groups.
2.4: Examples of Groups/Nongroups, Part I
Let's look at some examples of groups/nongroups.
2.5: Group Conventions and Properties
Before we discuss more examples, we present a theorem and look at some conventions we follow and notation we use when discussing groups in general; we also discuss some properties of groups.
2.6: Examples of Groups/Nongroups, Part II
Let's look at more examples of groups/nongroups.
2.7: Summaries of Groups We've Seen
When you see the following groups in the wild, you should assume they are equipped with the following default operations, unless otherwise noted. You should know what elements the groups contain, what their default operations are, their orders (and, if they're infinite, whether they're countably infinite or uncountable), and whether or not they are abelian.
2.8: Exercises, Part II
This page contains part II of the exercises for Chapter 2.