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The following propositional statement is  $\left(P \implies \left(Q \vee R\right)\right) \implies \left(\left(P \wedge Q \right)\implies R\right)$

1.    satisfiable but not valid
2.    valid
4.    None of the above
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It is false when P = T, Q = T, R = F

It is true (satisfiable) when P = T. Q = T, R = T
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what does it means '' not valid '' in option a ?????
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Tautology: A tautology is a proposition that is always ture.

ex: (p  v ~p)= T

ex: (p ^ ~p)=F

Contigency: A contigency is a proposition that is neither a tautology nor a contradiction.

ex: (p v q)----> ~r

* A propositional logic is said to be satisfiable if it is either a tautology or contigency.

* If logic is contradiction then it is said to be unsatisfiable.

* By contigency we means the logic can be ture or false.

* Contradiction is the unsatisfiable function.

* Statement is valid means tautology.

* Statement is not valid means not tautology.