SOLUTION: p->negation q , q disjunction r , negation s , negation r is a valid inference

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Question 1086495: p->negation q , q disjunction r , negation s , negation r is a valid inference
Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
1.  p->~q
2.  qvr
3.  ~s        /~r

It is not valid because: 

p->~q / qvr / ~s // ~r
F->FT   TvT   FT    FT   <--a case where the premises are 
                            all true and the conclusion false 

Edwin