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comment by mike
mike  ·  3504 days ago  ·  link  ·    ·  parent  ·  post: Pretty cool invitation in my mailbox today

I like the idea of "The Book". There's a lot of very elegant proofs in mathematics. One of my favorite is the proof that there is no greatest prime number. Assume there were a biggest prime, P. Now make the number 1 x 2 x 3 x 4 x 5 x .... x P plus 1. This number cannot be evenly divided by 2 or 3 or 4 or any number up to P because there will always be a remainder of 1 (that's the plus 1 on the end of the expression). That means the number must itself be prime or it must have a prime factor that is greater than P. Either way, we've shown that there must exist a prime greater than P, and we started by saying that P is the greatest prime. Therefore there is no greatest prime number.

For example, if you suppose the greatest prime number is 5, make a new number 1 x 2 x 3 x 4 x 5 + 1 = 121. Try dividing 121 by 2, 3, 4, and 5. There will always be a remainder of 1. That means 121's prime factors must be greater that 5 (they are: 11 and 11). So 5 is not the greatest prime.





mk  ·  3504 days ago  ·  link  ·  

FYI, you can use a \ to escape markup. i.e. +++.

mike  ·  3504 days ago  ·  link  ·  

Thanks, I was struggling with that! +

_refugee_  ·  3504 days ago  ·  link  ·  

Have you heard about Britain's infinite coastline? I'm sure you have, if you're telling me about this. But that's one I like.

Although your proof got messed up by the markup, I understand that there should be a plus at the beginning, and end, of your bolded section.

mike  ·  3504 days ago  ·  link  ·  

Yeah, coastlines are impossible to measure. Weeeeiiiirrrd.

OftenBen  ·  3504 days ago  ·  link  ·  

I thought 4.20 was yesterday?

_refugee_  ·  3504 days ago  ·  link  ·  

Boy ain't you heard the song errry day a holiday.