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Mathematics 8 Online
OpenStudy (anonymous):

Goldbach primer

OpenStudy (anonymous):

ok so can u write the definition that you know about Goldbach ?

OpenStudy (anonymous):

that would help me to explain when i know what you bassiclly know xD

ganeshie8 (ganeshie8):

Goldbach's conjecture states that every even integer greater than 2 can be expressed as the sum of two primes. Goldbach's conjecture is one of the oldest and best-known unsolved problems in number theory and in all of mathematics. http://en.wikipedia.org/wiki/Goldbach%27s_conjecture

ganeshie8 (ganeshie8):

is that good ?

OpenStudy (anonymous):

ok first line is enough \(\text{every even integer greater than 2 can be expressed as the sum of two primes. }\)

OpenStudy (anonymous):

that makes us think of 2 things :- 1- sum of 2 primes can represent unique even integer 2- an even number can be represented using at least one group of 2 primes agree so far ?

ganeshie8 (ganeshie8):

yes

ganeshie8 (ganeshie8):

yes but they may not cover all even numbers

OpenStudy (anonymous):

thats a good notation but note first i said they are infinite , however what im trying to do is seeing how much they can recover

ganeshie8 (ganeshie8):

ok

OpenStudy (anonymous):

remember my question \(\Large \Large \text {let P be the set of first nth odd primes } \\\Large P= \left \{ p_1,p2,....p_n \right\} \\ \Large \text{ and } \Large S= \left \{ p_i+p_j :\forall i,j\leq n \right \} \\ \Large \text{ then , show that there exist x(n) } \\ \Large \left \{ 6,8,10,.....,2p_{x(n)} \right \}\subseteq S \text { note that }\\ \Large x(n) \text{is a function of n } \\ \Large \text{with Range and domain of N and } x(n)<n \\ \text{ PS :- } \left \{ 6,8,10,.....,2p_{x(n)} \right \} =\left \{ 2\times 3 ,2\times 4,..., 2(p_{x(n ) }-1) ,2p_{x(n)} \right \}\)

OpenStudy (anonymous):

S is the group of all even that it can cover , ( agree ?)

OpenStudy (anonymous):

dont read it all i'll just explain bit by bit

ganeshie8 (ganeshie8):

i see lot of typoes in that

OpenStudy (anonymous):

ugh i see why u confused so a finite group of primes can represent a finite group of even numbers sorry for that :(

ganeshie8 (ganeshie8):

i was confused about goldbach from the start typoes will only make it worse

OpenStudy (anonymous):

hmm yeah sorry about it i meant to say -"so a finite group of primes can represent a finite group of even numbers " so for ur question -"yes but they may not cover all even numbers" -first i said they are "finite" , however what im trying to do is seeing how much they can recover

ganeshie8 (ganeshie8):

\[\Large \Large \text {let P be the set of first n odd primes } \\\Large P= \left \{ p_1,p_2,\ldots,p_n \right\} \\ \Large \text{ and } \Large S= \left \{ p_i+p_j : i,j\leq n \right \} \\ \Large \text{ then , show that there exists x(n) } \\ \Large \left \{ 6,8,10,.....,2p_{x(n)} \right \}\subseteq S \]

ganeshie8 (ganeshie8):

i get the definition of P and S sets i dont get x(n) and remaining part

OpenStudy (anonymous):

ok cool

OpenStudy (anonymous):

x(n) is just an increasing function , with respect to n properties 1- not constant 2- when n goes to infinity x(n) goes to infinity 3- domain and range of x(n) is natural numbers

ganeshie8 (ganeshie8):

ok

OpenStudy (anonymous):

so S as i said is the set of all evens can be represented by P group but when we order it , it might be discontinues at some values i'll show u an example

OpenStudy (anonymous):

\(\Large P=\left \{ 3,5,7,11 \right \}\\ \Large S=\left \{ 6,8,10,12,14,16,18,{\color{Red} 22} \right \} \)

ganeshie8 (ganeshie8):

so 20 is missing here ?

OpenStudy (anonymous):

so if we define a set V={6,8,.......,2k} k>2 when k=9 then \(V \subseteq S\) and V would be the largest set contained in S can be of this form

OpenStudy (anonymous):

yes , but i focused on discontinuity at 2 its discontinues (right ?)

OpenStudy (anonymous):

at 22 *

OpenStudy (anonymous):

agree so far ?

OpenStudy (anonymous):

if not tell me ur doubts

OpenStudy (anonymous):

now ,in general we cant know k that represent represent V which is the largest even ordered set contained in S since we get S with P elements only

ganeshie8 (ganeshie8):

V is a set of first k positive even integers ?

OpenStudy (anonymous):

yes contained in S

ganeshie8 (ganeshie8):

ok no i see why it is interesting

OpenStudy (anonymous):

since V is mystery for us (in General ) why cant we find another set contained in V ( so ovc it would be contained in S ) but have the largest element of 2*p such that p is prime ?

ganeshie8 (ganeshie8):

*now

OpenStudy (anonymous):

like for my example above p={3,5,7,11} S={6,8,10,12,14,16,18,22} V= {6,8,10,12,14,16,18} and let G be the set im talking about G= {6,8,10,12,14 }, 14=2*7

ganeshie8 (ganeshie8):

{6,8,10,12,14}

OpenStudy (anonymous):

yes !

OpenStudy (anonymous):

so in P set we have 4 elements ( n=4) and number 7 have the 3ed position so x(4)=3=4-1 (in this case )

OpenStudy (anonymous):

ok what other doubts u have so far ?

OpenStudy (anonymous):

i'll show u how this is equivelent to Goldbatch if u want to

ganeshie8 (ganeshie8):

``` so in P set we have 4 elements ( n=4) and number 7 have the 3ed position so x(4)=3=4-1 (in this case ) ```

ganeshie8 (ganeshie8):

i dont get this

ganeshie8 (ganeshie8):

P={3,5,7,11} P has 4 elements so that gives n = 4

OpenStudy (anonymous):

yes

OpenStudy (anonymous):

and G set have 2*7 if we mapped 7 to P 7 have the 3ed position ok ?

OpenStudy (anonymous):

instead of knowing k that evaluate V we need to know what is the prime that gives us G

OpenStudy (anonymous):

??

ganeshie8 (ganeshie8):

\(x(n) = n-1\) works always ?

OpenStudy (anonymous):

naa i talked about the existence of having such a function , so according to goldbach there exist , this is what im also trying to show x(n)=n-1 fail with n =5 i guess

OpenStudy (anonymous):

how ever , gap btw primes become larger there is small gap in small number but if we considered huge numbers gap sometimes is huge as well from here i had problem of choosing function since i need x(n) slowly increasing :) so with small n linear work with larger sqrt work with larger log work

OpenStudy (anonymous):

i hope u gt it any doubt im here , u can ask

ganeshie8 (ganeshie8):

nice

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