`1`.
`Lim \sqrt(9n^2+2n+1)-\sqrt(4n^2+1)`
`=Lim ((9n^2+2n+1)-(4n^2+1))/(\sqrt(9n^2+2n+1)+\sqrt(4n^2+1))`
`=Lim (5n^2+2n-2)/(\sqrt(9n^2+2n+1)+\sqrt(4n^2+1))`
`=Lim (5n+2-2/n)/(\sqrt(9+2/n+1/n^2)+\sqrt(4+1/n^2)`
`=Lim (+\infty)/(\sqrt9+\sqrt4)=+\infty`