Exercise:

EXISTS x(I) FORALL y(I) [P(OI) x EQUIV P y] EQUIV [EXISTS x Q(OI) x EQUIV FORALL y P y] EQUIV .EXISTS x FORALL y [Q x EQUIV Q y] EQUIV .EXISTS x P x EQUIV FORALL y Q y

You may not use ADVICE, but all other rules and commands are allowed.

Only book theorems may be ASSERTed as lemmas without proof.

For a complete list of book theorems, type PROBLEMS.

No more help available. Sorry.

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