## iran mathematical olympiad

Discussion on International Mathematical Olympiad (IMO)
mahathir
Posts: 24
Joined: Tue Feb 15, 2011 11:01 pm

### iran mathematical olympiad

if \$a,b,c,d\$ are natural numbers and \$ab=cd\$,then,prove that,\$a+b+c+d\$ cannot be a prime.

Masum
Posts: 592
Joined: Tue Dec 07, 2010 1:12 pm

### Re: iran mathematical olympiad

Try to prove the general one.
If \$ab=cd\$, prove that \$a^n+b^n+c^n+d^n\$ is not prime.
One one thing is neutral in the universe, that is \$0\$.

nayel
Posts: 268
Joined: Tue Dec 07, 2010 7:38 pm
Location: Dhaka, Bangladesh or Cambridge, UK

### Re: iran mathematical olympiad

The following method works for many problems of similar sort.
"Everything should be made as simple as possible, but not simpler." - Albert Einstein