Simplify [p∧ (¬(¬p v q)) ] v (p ∧ q) so that it become p, q, ¬p, or ¬q












2












$begingroup$


Had a question on a test that asked for us to simplify (using rules of inference) the following proposition: [p∧ (¬(¬p v q)) ] v (p ∧ q)

to p, q, or their negation (¬p, ¬q). Here is what I did:



1) [p∧ (¬(¬p v q)) ] v (p ∧ q)



2) [p∧ (p ∧ ¬q)) ] v (p ∧ q) DeMorgan's Law



3) [(p∧ p) ∧ ¬q] v (p∧ q) Associative law



4) [p ∧ ¬q] v (p∧ q) Idempotent law



Step 4 is where I got stuck. I didn't know what to do afterwards. So I substituted S= (p∧ q) and did distributive law



5) [p ∧ ¬q] v S



6) (S v p) ∧ (S v ¬q) Distributive law



7) [ (p∧q) v p ] ∧ [ (p∧q) v ¬q] Substitute S=(p∧q) back in



8) [ (pvp) ∧ (pvq) ] ∧ [ (¬q v p) ∧ (¬q v q) ] Distributive law



9) [ p ∧ (pvq) ] ∧ [ (¬q v p) ∧ T ] Idempotent law and Domination law



10) p ∧ (¬q v p) Absorption and Identity law



I stopped there. I didn't know how to further simplify step 10 into p, q, ¬p, or ¬q. I was thinking maybe absorption law? But p ∧ (¬q v p) is not the same as p ∧ (q v p), so I couldn't simplify it to p, correct? Can someone help me further simplify it? Do you think I will get most the marks for this question or was my approach completely wrong?










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$endgroup$












  • $begingroup$
    By the way, $pland (neg q lor p)$ can be immediately simplified to $p$ by what is known as the absorption law. See for example math.stackexchange.com/questions/2421690/… for some further reading.
    $endgroup$
    – Minus One-Twelfth
    Feb 16 at 1:03
















2












$begingroup$


Had a question on a test that asked for us to simplify (using rules of inference) the following proposition: [p∧ (¬(¬p v q)) ] v (p ∧ q)

to p, q, or their negation (¬p, ¬q). Here is what I did:



1) [p∧ (¬(¬p v q)) ] v (p ∧ q)



2) [p∧ (p ∧ ¬q)) ] v (p ∧ q) DeMorgan's Law



3) [(p∧ p) ∧ ¬q] v (p∧ q) Associative law



4) [p ∧ ¬q] v (p∧ q) Idempotent law



Step 4 is where I got stuck. I didn't know what to do afterwards. So I substituted S= (p∧ q) and did distributive law



5) [p ∧ ¬q] v S



6) (S v p) ∧ (S v ¬q) Distributive law



7) [ (p∧q) v p ] ∧ [ (p∧q) v ¬q] Substitute S=(p∧q) back in



8) [ (pvp) ∧ (pvq) ] ∧ [ (¬q v p) ∧ (¬q v q) ] Distributive law



9) [ p ∧ (pvq) ] ∧ [ (¬q v p) ∧ T ] Idempotent law and Domination law



10) p ∧ (¬q v p) Absorption and Identity law



I stopped there. I didn't know how to further simplify step 10 into p, q, ¬p, or ¬q. I was thinking maybe absorption law? But p ∧ (¬q v p) is not the same as p ∧ (q v p), so I couldn't simplify it to p, correct? Can someone help me further simplify it? Do you think I will get most the marks for this question or was my approach completely wrong?










share|cite|improve this question











$endgroup$












  • $begingroup$
    By the way, $pland (neg q lor p)$ can be immediately simplified to $p$ by what is known as the absorption law. See for example math.stackexchange.com/questions/2421690/… for some further reading.
    $endgroup$
    – Minus One-Twelfth
    Feb 16 at 1:03














2












2








2





$begingroup$


Had a question on a test that asked for us to simplify (using rules of inference) the following proposition: [p∧ (¬(¬p v q)) ] v (p ∧ q)

to p, q, or their negation (¬p, ¬q). Here is what I did:



1) [p∧ (¬(¬p v q)) ] v (p ∧ q)



2) [p∧ (p ∧ ¬q)) ] v (p ∧ q) DeMorgan's Law



3) [(p∧ p) ∧ ¬q] v (p∧ q) Associative law



4) [p ∧ ¬q] v (p∧ q) Idempotent law



Step 4 is where I got stuck. I didn't know what to do afterwards. So I substituted S= (p∧ q) and did distributive law



5) [p ∧ ¬q] v S



6) (S v p) ∧ (S v ¬q) Distributive law



7) [ (p∧q) v p ] ∧ [ (p∧q) v ¬q] Substitute S=(p∧q) back in



8) [ (pvp) ∧ (pvq) ] ∧ [ (¬q v p) ∧ (¬q v q) ] Distributive law



9) [ p ∧ (pvq) ] ∧ [ (¬q v p) ∧ T ] Idempotent law and Domination law



10) p ∧ (¬q v p) Absorption and Identity law



I stopped there. I didn't know how to further simplify step 10 into p, q, ¬p, or ¬q. I was thinking maybe absorption law? But p ∧ (¬q v p) is not the same as p ∧ (q v p), so I couldn't simplify it to p, correct? Can someone help me further simplify it? Do you think I will get most the marks for this question or was my approach completely wrong?










share|cite|improve this question











$endgroup$




Had a question on a test that asked for us to simplify (using rules of inference) the following proposition: [p∧ (¬(¬p v q)) ] v (p ∧ q)

to p, q, or their negation (¬p, ¬q). Here is what I did:



1) [p∧ (¬(¬p v q)) ] v (p ∧ q)



2) [p∧ (p ∧ ¬q)) ] v (p ∧ q) DeMorgan's Law



3) [(p∧ p) ∧ ¬q] v (p∧ q) Associative law



4) [p ∧ ¬q] v (p∧ q) Idempotent law



Step 4 is where I got stuck. I didn't know what to do afterwards. So I substituted S= (p∧ q) and did distributive law



5) [p ∧ ¬q] v S



6) (S v p) ∧ (S v ¬q) Distributive law



7) [ (p∧q) v p ] ∧ [ (p∧q) v ¬q] Substitute S=(p∧q) back in



8) [ (pvp) ∧ (pvq) ] ∧ [ (¬q v p) ∧ (¬q v q) ] Distributive law



9) [ p ∧ (pvq) ] ∧ [ (¬q v p) ∧ T ] Idempotent law and Domination law



10) p ∧ (¬q v p) Absorption and Identity law



I stopped there. I didn't know how to further simplify step 10 into p, q, ¬p, or ¬q. I was thinking maybe absorption law? But p ∧ (¬q v p) is not the same as p ∧ (q v p), so I couldn't simplify it to p, correct? Can someone help me further simplify it? Do you think I will get most the marks for this question or was my approach completely wrong?







discrete-mathematics logic propositional-calculus boolean-algebra






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share|cite|improve this question








edited Feb 16 at 4:01









Bram28

64.7k44793




64.7k44793










asked Feb 15 at 22:55









NevNev

466




466












  • $begingroup$
    By the way, $pland (neg q lor p)$ can be immediately simplified to $p$ by what is known as the absorption law. See for example math.stackexchange.com/questions/2421690/… for some further reading.
    $endgroup$
    – Minus One-Twelfth
    Feb 16 at 1:03


















  • $begingroup$
    By the way, $pland (neg q lor p)$ can be immediately simplified to $p$ by what is known as the absorption law. See for example math.stackexchange.com/questions/2421690/… for some further reading.
    $endgroup$
    – Minus One-Twelfth
    Feb 16 at 1:03
















$begingroup$
By the way, $pland (neg q lor p)$ can be immediately simplified to $p$ by what is known as the absorption law. See for example math.stackexchange.com/questions/2421690/… for some further reading.
$endgroup$
– Minus One-Twelfth
Feb 16 at 1:03




$begingroup$
By the way, $pland (neg q lor p)$ can be immediately simplified to $p$ by what is known as the absorption law. See for example math.stackexchange.com/questions/2421690/… for some further reading.
$endgroup$
– Minus One-Twelfth
Feb 16 at 1:03










2 Answers
2






active

oldest

votes


















4












$begingroup$

This is a common 'mistake': to Distribute when you should really 'Un-Distribute'. That is, you can see:



$(p land neg q) lor (p land q)$



as the result of applying Distribution to:



$p land (neg q lor q)$



But given that this is an equivalence, that means you can go the other way around as well (i.e. 'un-distribute' ... sometimes I call this 'reverse distribution' or 'factoring')



Note that from your last line we can do this as well:



$p land (neg q lor p) = (bot lor p) land (neg q lor p) = (bot land neg q) lor p = bot lor p =p$



Finally, the fact that $(p land q) lor (p land neg q)$ works out to just $p$ is such a common and handy equivalence that it has been given its own name:



Adjacency



$(p land q) lor (p land neg q) =p$



(and its dual form:) $(p lor q) land (p lor neg q)=p$



So, definitely put that one in your boolean algebra toolbox!






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Ohhhh you're totally right, that went right over my head. Judging by what I did for this question, do you think I'll lose all the marks?
    $endgroup$
    – Nev
    Feb 15 at 23:03






  • 1




    $begingroup$
    @nev all your steps were correct, and you did get close, so I would give you a good chunk of the points! :)
    $endgroup$
    – Bram28
    Feb 15 at 23:05



















4












$begingroup$

I'm going to use some shorthand notation: $pq$ for $p land q$, and $p + q$ for $p lor q$. Your proposition is $$p(neg(neg p + q)) + pq.$$ Distributing the negation on the left, we obtain $$p (neg (neg p + q)) + pq equiv pp(neg q) + pq.$$ Note that $pp equiv p$. This now gives us $$p(neg q) + pq.$$



We can "factor out" that $p$ to obtain $$p (neg q) + pq equiv p(neg q + q) equiv p,$$ and we're done.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Yes I totally see that now, thanks! I really hope I get at least some partial marks. I was supposed to "undo" the distribution rather than distribute again
    $endgroup$
    – Nev
    Feb 15 at 23:04












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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









4












$begingroup$

This is a common 'mistake': to Distribute when you should really 'Un-Distribute'. That is, you can see:



$(p land neg q) lor (p land q)$



as the result of applying Distribution to:



$p land (neg q lor q)$



But given that this is an equivalence, that means you can go the other way around as well (i.e. 'un-distribute' ... sometimes I call this 'reverse distribution' or 'factoring')



Note that from your last line we can do this as well:



$p land (neg q lor p) = (bot lor p) land (neg q lor p) = (bot land neg q) lor p = bot lor p =p$



Finally, the fact that $(p land q) lor (p land neg q)$ works out to just $p$ is such a common and handy equivalence that it has been given its own name:



Adjacency



$(p land q) lor (p land neg q) =p$



(and its dual form:) $(p lor q) land (p lor neg q)=p$



So, definitely put that one in your boolean algebra toolbox!






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Ohhhh you're totally right, that went right over my head. Judging by what I did for this question, do you think I'll lose all the marks?
    $endgroup$
    – Nev
    Feb 15 at 23:03






  • 1




    $begingroup$
    @nev all your steps were correct, and you did get close, so I would give you a good chunk of the points! :)
    $endgroup$
    – Bram28
    Feb 15 at 23:05
















4












$begingroup$

This is a common 'mistake': to Distribute when you should really 'Un-Distribute'. That is, you can see:



$(p land neg q) lor (p land q)$



as the result of applying Distribution to:



$p land (neg q lor q)$



But given that this is an equivalence, that means you can go the other way around as well (i.e. 'un-distribute' ... sometimes I call this 'reverse distribution' or 'factoring')



Note that from your last line we can do this as well:



$p land (neg q lor p) = (bot lor p) land (neg q lor p) = (bot land neg q) lor p = bot lor p =p$



Finally, the fact that $(p land q) lor (p land neg q)$ works out to just $p$ is such a common and handy equivalence that it has been given its own name:



Adjacency



$(p land q) lor (p land neg q) =p$



(and its dual form:) $(p lor q) land (p lor neg q)=p$



So, definitely put that one in your boolean algebra toolbox!






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Ohhhh you're totally right, that went right over my head. Judging by what I did for this question, do you think I'll lose all the marks?
    $endgroup$
    – Nev
    Feb 15 at 23:03






  • 1




    $begingroup$
    @nev all your steps were correct, and you did get close, so I would give you a good chunk of the points! :)
    $endgroup$
    – Bram28
    Feb 15 at 23:05














4












4








4





$begingroup$

This is a common 'mistake': to Distribute when you should really 'Un-Distribute'. That is, you can see:



$(p land neg q) lor (p land q)$



as the result of applying Distribution to:



$p land (neg q lor q)$



But given that this is an equivalence, that means you can go the other way around as well (i.e. 'un-distribute' ... sometimes I call this 'reverse distribution' or 'factoring')



Note that from your last line we can do this as well:



$p land (neg q lor p) = (bot lor p) land (neg q lor p) = (bot land neg q) lor p = bot lor p =p$



Finally, the fact that $(p land q) lor (p land neg q)$ works out to just $p$ is such a common and handy equivalence that it has been given its own name:



Adjacency



$(p land q) lor (p land neg q) =p$



(and its dual form:) $(p lor q) land (p lor neg q)=p$



So, definitely put that one in your boolean algebra toolbox!






share|cite|improve this answer











$endgroup$



This is a common 'mistake': to Distribute when you should really 'Un-Distribute'. That is, you can see:



$(p land neg q) lor (p land q)$



as the result of applying Distribution to:



$p land (neg q lor q)$



But given that this is an equivalence, that means you can go the other way around as well (i.e. 'un-distribute' ... sometimes I call this 'reverse distribution' or 'factoring')



Note that from your last line we can do this as well:



$p land (neg q lor p) = (bot lor p) land (neg q lor p) = (bot land neg q) lor p = bot lor p =p$



Finally, the fact that $(p land q) lor (p land neg q)$ works out to just $p$ is such a common and handy equivalence that it has been given its own name:



Adjacency



$(p land q) lor (p land neg q) =p$



(and its dual form:) $(p lor q) land (p lor neg q)=p$



So, definitely put that one in your boolean algebra toolbox!







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Feb 15 at 23:24

























answered Feb 15 at 22:59









Bram28Bram28

64.7k44793




64.7k44793












  • $begingroup$
    Ohhhh you're totally right, that went right over my head. Judging by what I did for this question, do you think I'll lose all the marks?
    $endgroup$
    – Nev
    Feb 15 at 23:03






  • 1




    $begingroup$
    @nev all your steps were correct, and you did get close, so I would give you a good chunk of the points! :)
    $endgroup$
    – Bram28
    Feb 15 at 23:05


















  • $begingroup$
    Ohhhh you're totally right, that went right over my head. Judging by what I did for this question, do you think I'll lose all the marks?
    $endgroup$
    – Nev
    Feb 15 at 23:03






  • 1




    $begingroup$
    @nev all your steps were correct, and you did get close, so I would give you a good chunk of the points! :)
    $endgroup$
    – Bram28
    Feb 15 at 23:05
















$begingroup$
Ohhhh you're totally right, that went right over my head. Judging by what I did for this question, do you think I'll lose all the marks?
$endgroup$
– Nev
Feb 15 at 23:03




$begingroup$
Ohhhh you're totally right, that went right over my head. Judging by what I did for this question, do you think I'll lose all the marks?
$endgroup$
– Nev
Feb 15 at 23:03




1




1




$begingroup$
@nev all your steps were correct, and you did get close, so I would give you a good chunk of the points! :)
$endgroup$
– Bram28
Feb 15 at 23:05




$begingroup$
@nev all your steps were correct, and you did get close, so I would give you a good chunk of the points! :)
$endgroup$
– Bram28
Feb 15 at 23:05











4












$begingroup$

I'm going to use some shorthand notation: $pq$ for $p land q$, and $p + q$ for $p lor q$. Your proposition is $$p(neg(neg p + q)) + pq.$$ Distributing the negation on the left, we obtain $$p (neg (neg p + q)) + pq equiv pp(neg q) + pq.$$ Note that $pp equiv p$. This now gives us $$p(neg q) + pq.$$



We can "factor out" that $p$ to obtain $$p (neg q) + pq equiv p(neg q + q) equiv p,$$ and we're done.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Yes I totally see that now, thanks! I really hope I get at least some partial marks. I was supposed to "undo" the distribution rather than distribute again
    $endgroup$
    – Nev
    Feb 15 at 23:04
















4












$begingroup$

I'm going to use some shorthand notation: $pq$ for $p land q$, and $p + q$ for $p lor q$. Your proposition is $$p(neg(neg p + q)) + pq.$$ Distributing the negation on the left, we obtain $$p (neg (neg p + q)) + pq equiv pp(neg q) + pq.$$ Note that $pp equiv p$. This now gives us $$p(neg q) + pq.$$



We can "factor out" that $p$ to obtain $$p (neg q) + pq equiv p(neg q + q) equiv p,$$ and we're done.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Yes I totally see that now, thanks! I really hope I get at least some partial marks. I was supposed to "undo" the distribution rather than distribute again
    $endgroup$
    – Nev
    Feb 15 at 23:04














4












4








4





$begingroup$

I'm going to use some shorthand notation: $pq$ for $p land q$, and $p + q$ for $p lor q$. Your proposition is $$p(neg(neg p + q)) + pq.$$ Distributing the negation on the left, we obtain $$p (neg (neg p + q)) + pq equiv pp(neg q) + pq.$$ Note that $pp equiv p$. This now gives us $$p(neg q) + pq.$$



We can "factor out" that $p$ to obtain $$p (neg q) + pq equiv p(neg q + q) equiv p,$$ and we're done.






share|cite|improve this answer









$endgroup$



I'm going to use some shorthand notation: $pq$ for $p land q$, and $p + q$ for $p lor q$. Your proposition is $$p(neg(neg p + q)) + pq.$$ Distributing the negation on the left, we obtain $$p (neg (neg p + q)) + pq equiv pp(neg q) + pq.$$ Note that $pp equiv p$. This now gives us $$p(neg q) + pq.$$



We can "factor out" that $p$ to obtain $$p (neg q) + pq equiv p(neg q + q) equiv p,$$ and we're done.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Feb 15 at 23:03









rwboglrwbogl

1,039717




1,039717












  • $begingroup$
    Yes I totally see that now, thanks! I really hope I get at least some partial marks. I was supposed to "undo" the distribution rather than distribute again
    $endgroup$
    – Nev
    Feb 15 at 23:04


















  • $begingroup$
    Yes I totally see that now, thanks! I really hope I get at least some partial marks. I was supposed to "undo" the distribution rather than distribute again
    $endgroup$
    – Nev
    Feb 15 at 23:04
















$begingroup$
Yes I totally see that now, thanks! I really hope I get at least some partial marks. I was supposed to "undo" the distribution rather than distribute again
$endgroup$
– Nev
Feb 15 at 23:04




$begingroup$
Yes I totally see that now, thanks! I really hope I get at least some partial marks. I was supposed to "undo" the distribution rather than distribute again
$endgroup$
– Nev
Feb 15 at 23:04


















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