# Proof Method and strategy

• May 20th 2009, 03:46 PM
micky_577
Proof Method and strategy
Hi,

I am not able to solve this by proper method. Please someone help.

Show that if n is perfect square then n-1 is not prime number for all interger n>4.

• May 20th 2009, 03:55 PM
Plato
Quote:

Originally Posted by micky_577
Show that if n is perfect square then n-1 is not prime number for all interger n>4.

Do you know this web-page?
• May 20th 2009, 04:02 PM
micky_577
Buddy,

I did not understand that. Is'nt prefect number is different than perfect squre? Please help me solve the question.

Thanks
• May 20th 2009, 04:06 PM
pickslides
I would argue that if n is a perfect square i.e $n=a^2$ then $n-1 = a^2-1$ , now $a^2-1$ can be factored into $(a-1)(a+1)$ and in turn so can n-1 so it cannot be prime.
• May 20th 2009, 04:56 PM
Plato
Quote:

Originally Posted by micky_577
Buddy,
I did not understand that. Is'nt prefect number is different than perfect squre? Please help me solve the question.

First of all, I doubt that I am your ‘buddy’. I have no idea who you could be.
From this reply it is clear that you don’t even understand your own question.
• May 20th 2009, 05:10 PM
micky_577
Please accept my sincere apology Plato. You are really correct in saying that I really did not understand question but I am trying learn man.

Thank you very much for your help.