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Which of the following well-formed formulas are equivalent?

1. $P \rightarrow Q$
2. $\neg Q \rightarrow \neg P$
3. $\neg P \vee Q$
4. $\neg Q \rightarrow P$
A,B and C are equivalent

1. P→Q    = P'+Q
2. ¬Q→¬P=Q+P'
3. ¬PVQ   =P'+Q
so A,B,C are equivalent .
selected
A,B,C are equavelent i.e. $P\rightarrow Q \equiv \sim P \vee Q$

A and C are equal because if $\rightarrow$ is true then Contradiction always true.
edited by
D is not equivalent
How D?
i was taken as  $\sim$(Q $\rightarrow$ P)
That is also not true.

I know that sir Or wil changes to And. thats why changed that.