I am trying to simplify the logic expression: $$p\lor q\lor(\neg p\land\neg q\land r)$$ with laws of logic to get: $$p\lor q\lor r$$ I have no idea how to get to the result by using the laws of logic. Help!


1 Answer 1


$$p\lor q\lor(\neg p\land\neg q\land r)$$ Use the distributive law: $$=(p\lor q\lor\neg p)\land(p\lor q\lor\neg q)\land(p\lor q\lor r)$$ Complementarity ($p\lor\neg p=1$) reduces the first two terms to 1: $$=1\land1\land(p\lor q\lor r)$$ Identity ($p\land1=p$) eliminates those 1s: $$=p\lor q\lor r$$

  • $\begingroup$ Thanks I’ll try that $\endgroup$
    – KClicque
    Jan 30, 2018 at 8:54
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    $\begingroup$ @KyleClicquennoi What? This is the answer. $\endgroup$ Jan 30, 2018 at 8:56
  • $\begingroup$ Yea sorry but I saw that there is $p \lor \lnot p$ and $q \lor \lnot q$ In the first two terms. Should I use the inverse law and then then the domination law or just the absorption law? $\endgroup$
    – KClicque
    Jan 30, 2018 at 9:04
  • $\begingroup$ Yes I do, I just did it differently. Using the commutative law on the first term then the inverse law on both terms to make it $p \lor T_0$ and $q \lor T_0$. I then used the domination law and then identify law to get where you are. It’s how my book wanted it $\endgroup$
    – KClicque
    Jan 30, 2018 at 9:28
  • $\begingroup$ Absorption. $a\vee(\neg a\wedge b)=a\vee b$ $\endgroup$ Jan 30, 2018 at 9:30

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