predicate logic doubt

Question

1) IS

P → Q ≡ Q → P

Satisfiable Or NOT?

Comments

Satisfiable but not valid.as for P,Q(T,T), returns true and for (T,F) returns false.

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$P\rightarrow Q\equiv Q\rightarrow P$

$\neg P\vee Q\equiv \neg Q\vee P$

$P\equiv T,Q\equiv T$

$T\equiv T$(Satisfiable)

$P\equiv F,Q\equiv F$

$T\equiv T$(Satisfiable)

$P\equiv T,Q\equiv F$

$F\equiv T$(Not Valid)

$P\equiv F,Q\equiv T$

$T\equiv F$(Not Valid)

Answer 1

It is satisfiable but not valid.