\(\left(\sqrt{2017}+\sqrt{2019}\right)^2=2017+2\sqrt{4072323}+2019=4036+2\sqrt{4072323}=4036+\sqrt{16289292}\)
\(\left(2\sqrt{2018}\right)^2=4.2018=4036+4036=4036+\sqrt{16289296}=4036+\sqrt{16289296}\)
Vì \(16289292< 16289296=>\sqrt{16289292}< \sqrt{16289296}\)
\(=>\left(\sqrt{2017}+\sqrt{2019}\right)^2< 2\sqrt{2018}\left(đpcm\right)\)