hai guyz, help me out if anyone is expert!

If p1, p2, p3.........pn are the first  n primes, show that p1p2p3......pn+1 is prime.

Greately appreciated.........if anybody can help........thankx

first make the question clear , i think this is not a possible case

say u take 1 , 2 and 3. However, 1x2x3 =6 is not a prime .

help me understand, i may be wrong.

 

I don't think 1 is a prime number. If you take 2 as the first prime number, then the question is correct.

The above statement is incorrect. Actually, it is not a prime.

Proof: (By counter-example)
2*3*5*7*11*13 + 1 = 30031  = 59 * 509

May be you are looking into the proof of infinitudes of prime. Euclid used the p1*p2*p3*....*pn +1 to prove the fact that there are infinite primes, but it does not mean that p1*p2*p3...*pn +1 has to be a prime number itself. That is the second part of the theorem.
Hope this helps.

Oops, Repost.

If you carefully look at the definition of a prime number, 1 is not a prime number. A prime number has to be divisible by 1 and itself i.e. a prime number has exactly two factors. Therefore the first prime number is 2. I don't how teachers in Nepal teach this in schools. I never knew this in school.

If you carefully look at the definition of a prime number, 1 is not a prime number. A prime number has to be divisible by 1 and itself i.e. a prime number has exactly two factors. Therefore the first prime number is 2. I don't how teachers in Nepal teach this in schools. I never knew this in school.

After you multiply by 2 then the result is not going to be prime.

thankx for everybody who responded to my questions.

I greatly appreciate you all.

thankx again

score

As far as I am concerned ..
let us suppose the first prime number P1 = 2
     P2 = 3
     P3 = 5
     P4 = 7
     P5 = 11
     P(n-1) where n is the set of real numbers
     Pn
     Pn+1 = (some prime nos) where n is the set of real nos..
thus from the Mathematical Induction theorem P1,P2,P3......Pn,Pn+1 is the set of prime numbers
For further information go to http://mathworld.wolfram.com/PrimeNumber.html

The question is wrong... you can never find a prime number which is a product of two same/different numbers unless you do (1*1=1) . In that also, there is some confusion about if people take 1 as prime or not.

Defination of prime says that , it is only divisible by itself or 1. So this question is wrong.

Sangfroid - The question is not wrong. If you look at the question carefully it clearly says that add one to the product of prime numbers. So a number is NOT a prime number if it is a product of prime numbers but is definitely a prime number if it is product of prime numbers plus 1.

ohh i thought it is an index of n....