c/m \(\sqrt{a+n}+\sqrt{a-n}< 2\sqrt{a}\)
\(\left(\sqrt{a+n}+\sqrt{a-n}\right)^2< \left(2\sqrt{a}\right)^2\)
\(\Leftrightarrow a+n+a-n+2\sqrt{a^2-n^2}< 4a\)
\(2a+2\sqrt{a^2-n^2}< 2a+2\sqrt{a^2}\)
\(2a+2\sqrt{a^2-n^2}< 4a\)
=>\(\sqrt{2001-1}+\sqrt{2001+1}< 2\sqrt{2001}\)
nên\(\sqrt{2000}-2\sqrt{2001}+\sqrt{2002}< 0\left(đpcm\right)\)