# Math Help - Show that for all integers r,s

1. ## Show that for all integers r,s

Quite straightforward, but it's proving somewhat frustrating for me.

Show that for all integers r,s with 2(r^2)+1= s, one of r and s must be divisble by 3.

2. Originally Posted by Jamot69
Quite straightforward, but it's proving somewhat frustrating for me.

Show that for all integers r,s with 2(r^2)+1= s, one of r and s must be divisble by 3.
If $r$ has form $3k+1$ then $2(r^2)+1$ is divisible by $3$, so $s$ is divisible by $3$. If $r$ has form $3k+2$ the same idea applies. Otherwise $r$ has form $3k$ but then there is nothing to show.