Is it correct?

$\neg$(a and b)=(not a) or (not b)

What ruleset can i look up for negations? Especially for "all", "if, then" statements.

  • 2
    $\begingroup$ That is correct. Quatifiers, when negated change to the other, ex $\forall$ becomes $\exists$. If P, the Q is equivalent to $\lnot$ P $\lor$ Q. You can use the negation of that to obtain the negation of the implication (if, then). $\endgroup$
    – RJM
    Oct 23, 2016 at 1:02

1 Answer 1


Yes, that's called De Morgan's Laws. This site has more rules about negations of logical connectives and this PDF should help you with negation of universal and existential quantifiers.

  • $\begingroup$ The site was very helpful! Thanks $\endgroup$
    – Cody
    May 4, 2020 at 6:11

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