Tui cũng là ARMY nè!!!!!!!!
\(-x+\sqrt{x}-2005+\sqrt{2006}\\ \Leftrightarrow-x+2\dfrac{\sqrt{x}}{2}-\dfrac{1}{4}-\dfrac{8019}{4}+\sqrt{2006}\\ \Leftrightarrow-\left(\sqrt{x}-\dfrac{1}{2}\right)^2-\dfrac{8019}{4}+\sqrt{2006}\le-\dfrac{8019}{4}+\sqrt{2006}\)
Vậy GTLN là\(-\dfrac{8019}{4}+\sqrt{2006}\) khi x=1/2