Is it possible to factorize, I'm trying to prove it isn't prime.
$x^4 + 15^x$
If for what values of x will the above be prime, also any general method of determining if a really large number is prime?
Thanks.
Is it possible to factorize, I'm trying to prove it isn't prime.
$x^4 + 15^x$
If for what values of x will the above be prime, also any general method of determining if a really large number is prime?
Thanks.
Definitely not a prime-- any odd value of x spoiling it.
As user 'ashley' has pointed, any odd number would damage it. To check the primality in general, there is a deterministic polynomial time algorithm. Please refer the famous paper which proves constructively to check if a number is prime or not is polynomial-time solvable. I don't know if something specific can be made to comment about your problem though.