I have been working on this problem for over an hour and I think I have simply missed something. I need some help. The rules I am allowed to use are the Basic Inference rules (MP, MT, HS, Simp, Conj, DS, Add, CD), the Replacement Rules (DN, Comm, Assoc, Dup, DeM, BE, Contrap, CE, Exp, Dist.), CP, IP, and EI, UI, EG, UG.
The problem is:
- ¬(∃x)(Axa ∧ ~Bxb)
- ¬(∃x)(Cxc ∧ Cbx)
- (∀x)(Bex → Cxf)
/∴ ¬(Aea ∧ Cfc)
Any help would be appreciated. Thanks.
Edit: Fixed the format of the question. The system is quantificational predicate logic. I've never called it anything else.