Ok, I've been doing a lot of reading, and these are my conclusions for the first two. Can someone tell me if I am "getting" them. As for the other three I am still working on them. Any further explanation is appreciated.
1. Ok. So I need to find a formula that is not a sentence, but contains a part that is a sentence.
A "sentence" is basically a formula that contains no free occurence of a variable.
So this has been offered:
AaFa v Gb
It is not a sentence because B is a free occurence, but it contains part that is a sentence (AaFa) because the variable is bound in both cases. There's no free occurence, and so this works for #1. Is my understanding sound?
2. Now I need to find a formula which contains occurences of a variable that are bound, and at least one that is free. So something might have been offered, but how bout this one? upside downAx[backwardsEy[Hy or Ga] therefore Jxy]