# Homework Set 3

**Due:** October 6 at the beginning of class

**Collaboration** in groups is ok, even encouraged. However, each of you *must* turn in a separate writeup. (But please do indicate with whom you collaborated to make life easier for the grader.)

**Section 1.6:** 9b is a tautology. Prove it by equivalences, do not use truth tables.

**Section 2.1:** 14a (do formally) (tricky, save for last) (Hint: write as ((2^k)^2-1^2), read the Wikipedia article about Mersenne Primes for more)

**Section 2.2:** 3bdf, 4a, 17, 19.

**Section 2.3:** 4a, 8b, 13.