Solutions to this week's homework have been posted on the schedule page (as HW7&8).

Please study all those that you had difficulty with, but pay particular attention to problem 7, which is an invalid proof that fails to terminate.  I realized after class that my semantic proof of the invalidity of this argument was hasty, so I've provided the explicit proof underneath.

Here is Tuesday's homework. Turn in the blue ones. Probably Thursday's homework will come from the same sheet, but it will like be expanded to include a few more problems.

To do this sheet you must know all four inference rules for the quantifiers. We have not yet reviewed existential elimination in class, so be sure to engage the video and/or slides and/or text regarding this rule before attempting the homework.  You will also find it helpful to know the derived rules we discussed in class.

Note: The videos on the inference rules for quantifiers make use of some of the derived rules but also the equivalence DN. I have explained how this works on the top of the homework page and you are free to use it even though we have not yet introduced equivalences in general.