Concept : Sum of two primes

[n00bpron00bpron00b]

Hi Tommy,

According to the number properties book,

If the sum of two primes is even then both primes have to be odd (odd + odd = even). But there could also be a case wherein both the primes are even and yet the sum is even (2 + 2 = 4).

Is this something that I should keep in mind, especially for problems where a contradiction is required.

Thanks.
noob

[tommywallach]

Hey Noob,

Hmm. The book actually says:

"...the sum of any two primes will be even, unless one of those primes is the number two." So it's very clear about the exception.

-t

[n00bpron00bpron00b]

Hi Tommy,

"...the sum of any two primes will be even, unless one of those primes is the number two." So it's very clear about the exception.

Thank you for pointing it out. I guess I have overlooked that important piece of information.

noob

[tommywallach]

No problem!