Go back
Every prime is odd

Every prime is odd

Posers and Puzzles

F

Joined
11 Nov 05
Moves
43938
Clock
16 Aug 06
Vote Up
Vote Down

This is a thought that I've had for a time.

Every prime is odd. Odd, isn't it?
And I can prove it. Does anyone know how?

T

Joined
21 Jul 06
Moves
0
Clock
16 Aug 06
1 edit
Vote Up
Vote Down

Originally posted by FabianFnas
This is a thought that I've had for a time.

Every prime is odd. Odd, isn't it?
And I can prove it. Does anyone know how?
Yes, you must first prove that 2 is odd. And the rest is easy.

F

Joined
11 Nov 05
Moves
43938
Clock
16 Aug 06
Vote Up
Vote Down

Originally posted by ThudanBlunder
Yes, you must first prove that 2 is odd. And the rest is easy.
Well, 2 is prime and even, thats a fact. The proof that every prime is odd doesn't take that into consideration. Just a minor detail... ;-)

Does anyone know the proof?

t

Joined
03 May 06
Moves
1886
Clock
16 Aug 06
Vote Up
Vote Down

Because all even numbers are divisable by 2....

a
Enola Straight

mouse mouse mouse

Joined
16 Jan 05
Moves
12804
Clock
16 Aug 06
Vote Up
Vote Down

If you mean "odd" as in "unusual", it's quite easy to prove.

F

Joined
11 Nov 05
Moves
43938
Clock
16 Aug 06
Vote Up
Vote Down

Nono, unusual is odd enough but here I mean odd as not being even as matematicians do.

thespacemonkey says:
"Because all even numbers are divisable by 2...."

Well, either you give a glimpse that you know the proof or you're not. This I have to think over.

(*think, think, think*) What about two itself? (*think, think, think*)

Yes, you are right. The statement of yours that "all even nubers are evenly divisable with two" has the same kind of proof that the statement "all primes are odd" has. Well done.

B
Non-Subscriber

RHP IQ

Joined
17 Mar 05
Moves
1345
Clock
16 Aug 06
Vote Up
Vote Down

The proof that you are even odder is contained within this very thread.

t

Joined
03 May 06
Moves
1886
Clock
16 Aug 06
Vote Up
Vote Down

Well as the definition of an even number is a number that is divisible by 2, and the definition of a prime number is a number only divisible by 1 and itself, if a number is not 2 (as you decided to take it out of the prime numbers for some reason) it has to be odd to be prime.

F

Joined
11 Nov 05
Moves
43938
Clock
16 Aug 06
1 edit
Vote Up
Vote Down

I didn't think far enough here, sorry for that.

If thespacemonkey had said:
"All even numbers are divisable by 2 and still gives an even result"
then the proof of this would be very like the proof of that every prime is odd.

Please forgive me of this lapsus.

Let's stick to the statement that all primes are odd.

T

Joined
21 Jul 06
Moves
0
Clock
16 Aug 06
Vote Up
Vote Down

Originally posted by FabianFnas
Let's stick to the statement that all primes are odd.
...unless they are even.

iamatiger

Joined
26 Apr 03
Moves
26771
Clock
16 Aug 06
Vote Up
Vote Down

Originally posted by FabianFnas
I didn't think far enough here, sorry for that.

If thespacemonkey had said:
"All even numbers are divisable by 2 and still gives an even result"
then the proof of this would be very like the proof of that every prime is odd.

Please forgive me of this lapsus.

Let's stick to the statement that all primes are odd.
Equally, no primes are divisible by 3 either.

t

Joined
03 May 06
Moves
1886
Clock
16 Aug 06
Vote Up
Vote Down

Maybe it's because it's early in the morning, maybe it's because I am missing something, maybe it's because I am thick as pig excriment. I don't get exactly what you are asking to be proved.

X
Cancerous Bus Crash

p^2.sin(phi)

Joined
06 Sep 04
Moves
25076
Clock
17 Aug 06
1 edit
Vote Up
Vote Down

Originally posted by iamatiger
Equally, no primes are divisible by 3 either.
And now by induction I will expand this proof.

A prime P will not be divisible by any n where n != 1 or p.
Already it has been shown for n=2 and n=3. Therefore all I have to show is that if the nth case is true then the n+1th case is true.

So if no A exists such that n*A = p then then no B must exist such that (n+1)*B = P. Utilizing the properties of primes we can show that no B exists that divides P except P and 1.

Therefore the n+1th case is true.

Therefore by induction we have shown that a prime number is only divisible by 1 and itself.

(Seriously what's going on in this thread?)

F

Joined
11 Nov 05
Moves
43938
Clock
17 Aug 06
Vote Up
Vote Down

The first 10 primes is as follows: 2, 3, 5, 7, 11, 13, 17, 23, 29,31.
Of theese 10 first primes only one is even, the rest is odd. Right?
The ratio of odd primes of the ten first is 9/10=90%. Right?

Do anyone se what I'm aiming at?

X
Cancerous Bus Crash

p^2.sin(phi)

Joined
06 Sep 04
Moves
25076
Clock
17 Aug 06
Vote Up
Vote Down

Originally posted by FabianFnas
The first 10 primes is as follows: 2, 3, 5, 7, 11, 13, 17, 23, 29,31.
Of theese 10 first primes only one is even, the rest is odd. Right?
The ratio of odd primes of the ten first is 9/10=90%. Right?

Do anyone se what I'm aiming at?
A proof that 100% of primes are odd is not the same as proof that all primes are odd.

Cookies help us deliver our Services. By using our Services or clicking I agree, you agree to our use of cookies. Learn More.