Question

prove that every prim p>2 can be writing in the form of 2n+1 for n>0 ,n number natural,so p-1=2n --- p-1 --- even,because p is odd.

so p>2 --- than p>=3
p is prim,p>2 so than p is even so p=2k+1,where k=1,2,3,...,n.
so p=2k+1 --- subtract 1 from both sides,than
p-1=2k
2n=p-1=2k so
2n=2k --- divide both sides by 2
n=k
- so for every p prims there are n>=1,n natural ,
such that p=2n+1

- is this correct,right ?

Answer 1

By division algorithm, every integer can be written in the form 2k or 2k+1.Primes are those which do not have ANY factors except 1 and itself.Thus, the form 2k is out of bounds for k>1. Thus, every prime >2 is of the form 2k+1

Answer 2

ok but how to prove it this ?

Answer 3

That IS the proof!

Answer 4

what ? can you write this here ?

Answer 5

1.Every int can be written as 2k or 2k+1.
2.The int 2k is divisible by 2.Thus it is not a prime for k>1
3.The conclusion follows.