Comments:

range from 20 to 100 with average of 82.5, 22 homeworks submitted

25 points for each problem

3-38 was good, but some people got their answer simply by establishing a
pattern. Although the problem did not use the word "prove" I still thought one
ought to prove that their answer is correct, so I expected a good proof by
induction. (Although if you only did a pattern, I made the deduction relatively
minor). I couple people seem to think that establishing a proof by induction
means making a pattern but that is not true. A few people got careless and got
Fn insead of Fn+1, but they ought to know better.

3-39 and 3-40 Some people's proofs weren't thorough enough and had some
hard-to-follow reasoning, but these were mostly good. Remember, even if you
know what you're talking about, you need to present it in a way comprehensible
to the grader in order to get points.

3-42 was nice.