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Mathematics 17 Online
OpenStudy (anonymous):

If you have (p&q) -> r, can I use the rule of conjunctive simplification to reduce the p&q to just p?

OpenStudy (anonymous):

this is discrete mathematics btw

OpenStudy (king):

I think so....Yes?

OpenStudy (jamesj):

If you're asking whether (p&q) -> r implies p -> r then the answer is most definitely no. E.g., p = (x=1), q = (y=x), r = (y=1)

OpenStudy (anonymous):

oh darn you are right.. any way to get (p&q) -> r using q to become p->r?

OpenStudy (jamesj):

Well ((p^q) -> r) = ~((p^q)^-r) = ~(p^q)v r = (~p v ~q) v r = ~p v (~q v r) = ~p v ~(q ^ ~r) = ~p v (q -> r) = ~ (p^~(q -> r)) = p -> (q -> r) So yes I.e., p^q -> r is equivalent to p -> (q ->r) and by symmetry of the argument also equivalent to q -> (p -> r)

OpenStudy (anonymous):

you misread my question I was trying to get it to p->r but thanks for trying

OpenStudy (jamesj):

In short, if the only thing you have is ( p^q -> r), then you cannot conclude (p -> r)

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