- #1
VinnyCee
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Homework Statement
Use rules of inference to show that if [tex]\forall\,x\,(P(x)\,\vee\,Q(x))[/tex] and [tex]\forall\,x\,((\neg\,P(x)\,\wedge\,Q(x))\,\longrightarrow\,R(x))[/tex] are true, then [tex]\forall\,x\,(\neg\,R(x)\,\longrightarrow\,P(x))[/tex] is true.
Homework Equations
Universal instantiation, Disjunctive syllogism, Conjunction.
The Attempt at a Solution
1) [tex]\forall\,x\,(P(x)\,\vee\,Q(x))[/tex] Premise
2) [tex]P(a)\,\vee\,Q(a)[/tex] Universal instantiation of (1)
3) [tex]\neg\,P(a)[/tex] Disjunctive syllogism of (2)
4) [tex]\forall\,x\,((\neg\,P(x)\,\wedge\,Q(x))\,\longrightarrow\,R(x))[/tex] Premise
5) [tex](\neg\,P(a)\,\wedge\,Q(a))\,\longrightarrow\,R(a)[/tex] Universal instantiation of (4)
6) [tex]R(a)[/tex] Modus Ponens of (5)
Here I am stuck, any suggestions?