(1) 

(2)

lim(2n-√4n^2+an+3)*(2n+√4n^2+an+3)/(2n+√4n^2+an+3) n→∞,

=lim(4n^2-4n^2-an-3)/(2n+√4n^2+an+3)

=-a/4=1  , a=-4