# Math 31: Abstract Algebra

## homework

I mean the word proof not in the sense of the lawyers, who set two half proofs equal to a whole one, but in the sense of a mathematician, where ½ proof = 0, and it is demanded for proof that every doubt becomes impossible.
--Carl Friedrich Gauss

Weekly problem sets will be posted every Wednesday, and due the following Wednesday (unless otherwise noted) before the start of class. Your write-ups should be neat, legible, and stapled. Proofs should be written in complete sentences. In general, late homework will not be accepted for a grade, and never without prior arrangement. Illness and family emergency are the two main reasons why an extension on homework may be granted.

Challenge problems will posted regularly throughout the term. The challenge problems will be more difficult than those on your problem sets. In general, challenge problems require proofs. You will solve ten challenge problems by the end of the quarter. To encourage you to be thinking about these challenge problems, two solutions are due by October 1st, four additional solutions are due by October 29th, and the final four problems are due by November 12. Turn in your challenge problem solutions on a separate sheet of paper from your problem set solutions.

collaboration

I strongly encourage you to collaborate with others on your problems sets and challenge problems. When learning difficult mathematics, it is helpful to discuss ideas and confusions with your classmates. If you choose to collaborate (please do!), keep the following guidelines in mind:

• The solutions that you turn in should be written up by you, using your own words. Freely brainstorm with others, but when you put those ideas down on paper, you should do so individually.
• If you have worked with others on a particular problems, make a note of it in your write up. Simply write something such as "Worked with James on this one" in the margin of your write up.

Here are several examples of acceptable levels of collaboration.

Unfortunately, I must assign you a number to measure your comprehension of course material. In mathematics, a proof is either correct, or not. On the other hand, a proof can be almost right, but there is some small detail that keeps it from being an airtight argument. Each problem will be graded on a scale of 0 to 5, depending the extent to which the proof deviates from being correct. In general, a solution will loose 1 point for a minor defect and 2 points for a major defect. You will never loose points for being creative.

Here are is an example of a proof in which a few details are omitted, and how it could be modified to become correct.

### problem sets

1. Your first problem set has been posted. It is due at the beginning of class on Wednesday, September 19. If you're interested in typing your homework, here is the associated tex file.

2. Your second problem set is now ready. It is due at the beginning of class on Wednesday, September 26. Have at it. Here is the tex file.

3. Your third problem set is now ready. It will be due on Wednesday, October 3. Here is the tex file. I have typed up solutions for problem set 3.

4. Your fourth problem set is now ready. Though it is slightly longer than your past problem sets, it is easier (in your instructor's opinion). Here is the tex file. Here are solutions.

5. Another problem set. This will be your final problem set before your midterm. Here is the tex file. Select solutions.

6. Your sixth problem set, and your first dealing with rings. It'll be due on Halloween. There are some especially interesting problems on this one. Here is the tex file. Here are some solutions.

7. Your seventh problem set, and your last problem set of the term. It's due on November 7th. Here is the tex file. Select solutions.

### challenge problems

A list of 20 challenge problems can be found here. The pdf was last updated on November 7th. Your final bunch of challenge problems are due by Monday November 12th.