0

This one is driving me crazy. I don't understand most keys for de morgan, modus ponens, etc, so please abbreviate if possible? EX: DM, MP, SIMP, HS, Conj, Imp (material Implication). Thank you anybody who can help out! v or, ~ not, ^ and, > if...then, => if and only if (bi-conditional).

- P>(RvS)
- ~[(~Pv~Q)v(Rv~L)]

and the conclusion is S.

So:

~(~Pv~Q)v~(Rv~L) 2,DM

(PvQ)v(~RvL) 3,DM

~(PvQ)>(~RvL 4,IMP

~Pv(RvS) 1, IMP

(~PvR)vS 6, ASSOC

(Rv~P)vS

~Rv~P)>S

(~RvP)>S

What's getting me is I can't isolate a variable that helps complete the conclusion that S is so! I have other notes, too, but can't place it. There is no other info than the first 2 lines. I can't isolate a truth because they're all disjunctions (v) or conditionals (>). Am I missing an Addition, Modus Tolens, or Modus Ponens somewhere? I was thinking maybe a double negation, but I can't figure this out after working on it almost all day yesterday. Final question on a Logic exam already passed. Hope this makes sense?

You're using De Morgan incorrectly. The disjunction should change to conjunction. – Eliran – 2019-07-27T22:56:21.510

Think i got it solved – Mick – 2019-07-28T00:34:52.560