4.2, due on September 30

1. The hardest part for me is probably keeping track of which polynomials are which in the proofs. That's mostly because the notation for polynomials is a bit more complicated in general than for numbers.

2.  I thought it was interesting that there is always only one gcd for any two polynomials, even though the gcd is simply the common divisor with the highest degree.  It's not immediately obvious that there is only one monic polynomial that satisfies this definition, but it ends up being true.