Ta có 0,7(\(19^{5^{2007}}\)+\(2007^{2008^{2009}}\))= \(\frac{7\left(19^{5^{2007}}+2007^{2008^{2009}}\right)}{10}\)
\(19^{5^{2007}}\)= \(19^{\left(............5\right)}\)= (..............9)
\(2007^{2008^{2009}}\)= 20074k= (............1)
=> \(19^{5^{2007}}\)+ \(2007^{2008^{2009}}\)= (............0)
=> 7(\(19^{5^{2007}}\)+ \(2007^{2008^{2009}}\)) = (............0) \(⋮\)10
Vậy 0,7(\(19^{5^{2007}}\)+\(2007^{2008^{2009}}\)) là một số tự nhiên