proving that $a^6 in L$ (tricky) (pumping lemma)











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i've encountered a quite tricky question that i don't understand, and would appreciate your help with:



it is said that by the pumping lemma, for a certain L there exists(guarenteed) n=2. also known that $aa in L$. prove that $a^6 in L$



so from what i understand, because it is guranteed that for some L, because of the pumping lemma, n=2, it means that for a word $w in L$, w can be represented as such: w=abc, so that $|ab| leq n$, $|b| geq 1$ and for every $i in N$: $ab^ic in L$. so if $aa in L$, then the boundary(first condition) is n=2 as given, but does it mean that it can only one letter, so that $a^6 in L$? basically, i think that i should be using the third condition(for every $i in N$ $ab^ic in L$, but how can i ommit a and c so i could show that i=6, i.e $a^6 in L$



tried to explain the question and my way of thinking the best i could. how can i show that $a^6 in L$?










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    Think of what $b$ can be in your situation for the word $aa$. Remember that if $n=2$ is the pumping constant, the word $aa$ satisfies the initial conditions to be pumped.
    – NL1992
    Dec 2 at 15:30










  • i might be very confused, but b should be a? really confused and would appreciate your help with it
    – mathnoobie
    Dec 2 at 20:24















up vote
0
down vote

favorite
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i've encountered a quite tricky question that i don't understand, and would appreciate your help with:



it is said that by the pumping lemma, for a certain L there exists(guarenteed) n=2. also known that $aa in L$. prove that $a^6 in L$



so from what i understand, because it is guranteed that for some L, because of the pumping lemma, n=2, it means that for a word $w in L$, w can be represented as such: w=abc, so that $|ab| leq n$, $|b| geq 1$ and for every $i in N$: $ab^ic in L$. so if $aa in L$, then the boundary(first condition) is n=2 as given, but does it mean that it can only one letter, so that $a^6 in L$? basically, i think that i should be using the third condition(for every $i in N$ $ab^ic in L$, but how can i ommit a and c so i could show that i=6, i.e $a^6 in L$



tried to explain the question and my way of thinking the best i could. how can i show that $a^6 in L$?










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  • 1




    Think of what $b$ can be in your situation for the word $aa$. Remember that if $n=2$ is the pumping constant, the word $aa$ satisfies the initial conditions to be pumped.
    – NL1992
    Dec 2 at 15:30










  • i might be very confused, but b should be a? really confused and would appreciate your help with it
    – mathnoobie
    Dec 2 at 20:24













up vote
0
down vote

favorite
1









up vote
0
down vote

favorite
1






1





i've encountered a quite tricky question that i don't understand, and would appreciate your help with:



it is said that by the pumping lemma, for a certain L there exists(guarenteed) n=2. also known that $aa in L$. prove that $a^6 in L$



so from what i understand, because it is guranteed that for some L, because of the pumping lemma, n=2, it means that for a word $w in L$, w can be represented as such: w=abc, so that $|ab| leq n$, $|b| geq 1$ and for every $i in N$: $ab^ic in L$. so if $aa in L$, then the boundary(first condition) is n=2 as given, but does it mean that it can only one letter, so that $a^6 in L$? basically, i think that i should be using the third condition(for every $i in N$ $ab^ic in L$, but how can i ommit a and c so i could show that i=6, i.e $a^6 in L$



tried to explain the question and my way of thinking the best i could. how can i show that $a^6 in L$?










share|cite|improve this question









New contributor




mathnoobie is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











i've encountered a quite tricky question that i don't understand, and would appreciate your help with:



it is said that by the pumping lemma, for a certain L there exists(guarenteed) n=2. also known that $aa in L$. prove that $a^6 in L$



so from what i understand, because it is guranteed that for some L, because of the pumping lemma, n=2, it means that for a word $w in L$, w can be represented as such: w=abc, so that $|ab| leq n$, $|b| geq 1$ and for every $i in N$: $ab^ic in L$. so if $aa in L$, then the boundary(first condition) is n=2 as given, but does it mean that it can only one letter, so that $a^6 in L$? basically, i think that i should be using the third condition(for every $i in N$ $ab^ic in L$, but how can i ommit a and c so i could show that i=6, i.e $a^6 in L$



tried to explain the question and my way of thinking the best i could. how can i show that $a^6 in L$?







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edited Dec 2 at 15:29









saulspatz

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asked Dec 2 at 14:48









mathnoobie

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  • 1




    Think of what $b$ can be in your situation for the word $aa$. Remember that if $n=2$ is the pumping constant, the word $aa$ satisfies the initial conditions to be pumped.
    – NL1992
    Dec 2 at 15:30










  • i might be very confused, but b should be a? really confused and would appreciate your help with it
    – mathnoobie
    Dec 2 at 20:24














  • 1




    Think of what $b$ can be in your situation for the word $aa$. Remember that if $n=2$ is the pumping constant, the word $aa$ satisfies the initial conditions to be pumped.
    – NL1992
    Dec 2 at 15:30










  • i might be very confused, but b should be a? really confused and would appreciate your help with it
    – mathnoobie
    Dec 2 at 20:24








1




1




Think of what $b$ can be in your situation for the word $aa$. Remember that if $n=2$ is the pumping constant, the word $aa$ satisfies the initial conditions to be pumped.
– NL1992
Dec 2 at 15:30




Think of what $b$ can be in your situation for the word $aa$. Remember that if $n=2$ is the pumping constant, the word $aa$ satisfies the initial conditions to be pumped.
– NL1992
Dec 2 at 15:30












i might be very confused, but b should be a? really confused and would appreciate your help with it
– mathnoobie
Dec 2 at 20:24




i might be very confused, but b should be a? really confused and would appreciate your help with it
– mathnoobie
Dec 2 at 20:24










1 Answer
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0
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Ok, let's fix some easier notation:



We say that a language $L$ satisfies the pumping lemma for $p>0$ if for any word $win L$ with $|w|geq p$ we have that $w=xyz$ with the properties:
$$1. pgeq |xy|, |y|>0
$$

$$2. forall iin Bbb N: xy^izin L
$$

So in our case, $y$ (which is being 'pumped') would either be $a$ or $aa$.






share|cite|improve this answer








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NL1992 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.


















  • so basically after asserting that y is either a or aa, is it sufficient to say that because of this and the properties of the pumping lemma, $a^6 in L$?
    – mathnoobie
    Dec 2 at 21:34










  • Yes, and you can divide to cases and prove it directly if you want to.
    – NL1992
    Dec 2 at 21:38











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Ok, let's fix some easier notation:



We say that a language $L$ satisfies the pumping lemma for $p>0$ if for any word $win L$ with $|w|geq p$ we have that $w=xyz$ with the properties:
$$1. pgeq |xy|, |y|>0
$$

$$2. forall iin Bbb N: xy^izin L
$$

So in our case, $y$ (which is being 'pumped') would either be $a$ or $aa$.






share|cite|improve this answer








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  • so basically after asserting that y is either a or aa, is it sufficient to say that because of this and the properties of the pumping lemma, $a^6 in L$?
    – mathnoobie
    Dec 2 at 21:34










  • Yes, and you can divide to cases and prove it directly if you want to.
    – NL1992
    Dec 2 at 21:38















up vote
0
down vote













Ok, let's fix some easier notation:



We say that a language $L$ satisfies the pumping lemma for $p>0$ if for any word $win L$ with $|w|geq p$ we have that $w=xyz$ with the properties:
$$1. pgeq |xy|, |y|>0
$$

$$2. forall iin Bbb N: xy^izin L
$$

So in our case, $y$ (which is being 'pumped') would either be $a$ or $aa$.






share|cite|improve this answer








New contributor




NL1992 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.


















  • so basically after asserting that y is either a or aa, is it sufficient to say that because of this and the properties of the pumping lemma, $a^6 in L$?
    – mathnoobie
    Dec 2 at 21:34










  • Yes, and you can divide to cases and prove it directly if you want to.
    – NL1992
    Dec 2 at 21:38













up vote
0
down vote










up vote
0
down vote









Ok, let's fix some easier notation:



We say that a language $L$ satisfies the pumping lemma for $p>0$ if for any word $win L$ with $|w|geq p$ we have that $w=xyz$ with the properties:
$$1. pgeq |xy|, |y|>0
$$

$$2. forall iin Bbb N: xy^izin L
$$

So in our case, $y$ (which is being 'pumped') would either be $a$ or $aa$.






share|cite|improve this answer








New contributor




NL1992 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









Ok, let's fix some easier notation:



We say that a language $L$ satisfies the pumping lemma for $p>0$ if for any word $win L$ with $|w|geq p$ we have that $w=xyz$ with the properties:
$$1. pgeq |xy|, |y|>0
$$

$$2. forall iin Bbb N: xy^izin L
$$

So in our case, $y$ (which is being 'pumped') would either be $a$ or $aa$.







share|cite|improve this answer








New contributor




NL1992 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









share|cite|improve this answer



share|cite|improve this answer






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answered Dec 2 at 21:09









NL1992

718




718




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  • so basically after asserting that y is either a or aa, is it sufficient to say that because of this and the properties of the pumping lemma, $a^6 in L$?
    – mathnoobie
    Dec 2 at 21:34










  • Yes, and you can divide to cases and prove it directly if you want to.
    – NL1992
    Dec 2 at 21:38


















  • so basically after asserting that y is either a or aa, is it sufficient to say that because of this and the properties of the pumping lemma, $a^6 in L$?
    – mathnoobie
    Dec 2 at 21:34










  • Yes, and you can divide to cases and prove it directly if you want to.
    – NL1992
    Dec 2 at 21:38
















so basically after asserting that y is either a or aa, is it sufficient to say that because of this and the properties of the pumping lemma, $a^6 in L$?
– mathnoobie
Dec 2 at 21:34




so basically after asserting that y is either a or aa, is it sufficient to say that because of this and the properties of the pumping lemma, $a^6 in L$?
– mathnoobie
Dec 2 at 21:34












Yes, and you can divide to cases and prove it directly if you want to.
– NL1992
Dec 2 at 21:38




Yes, and you can divide to cases and prove it directly if you want to.
– NL1992
Dec 2 at 21:38










mathnoobie is a new contributor. Be nice, and check out our Code of Conduct.










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