Question

Hi can someone help me please? Show that for every non-zero integer n , the number n^2+3n+2 is not prime

Answer 1

@liltish007

Answer 2

check tow cases
1_ if n is odd
n=2k+1
(2k+1)^2+3(2k+1)+2
=4k^2+4k+1+6k+3+2
=4k^2+10k+6=2(2k^2+5k+3) is even so not prime
2_if n is even
n=2k
(2k)^2+3(2k)+2
=4k^2+6k+2=2(2k^2+3k+1) is even not prime

Answer 3

The usage of these 2 cases can be used to prove any non prime numbers?

Answer 4

And for curiosities sake, to determine a prime number in for example prove that f(n)= n-1 is a prime number Can i still use those cases ?

Answer 5

hmmm not all its depand
but i guess it will help u a lot
its kind of number theory ..
so u can prove if a fun is always not prime
but u cant prove if its always prime
f(n)=n-1 is not always prime for example
n=9
f(9)=9-1=8 not prime
or n=4
f(4)=4-1=3 prime

Answer 6

I think I get it.. I'll go practice some more .. Thanks for the help you really saved my life :)

Answer 7

np .. ur wlc lol !