Rewrite $ 4n^{2}-25 $ as:
$$ 4n^{2}-25 = (2n)^2 - (5)^2 $$Now we can apply the difference of squares formula.
$$ I^2 - II^2 = (I - II)(I + II) $$After putting $ I = 2n $ and $ II = 5 $ , we have:
$$ 4n^{2}-25 = (2n)^2 - (5)^2 = ( 2n-5 ) ( 2n+5 ) $$