ĐKXĐ: \(x\ge2005\)
\(M=x-2005-\sqrt{x-2005}+2005=x-2005-2.\dfrac{1}{2}\sqrt{x-2005}+\dfrac{1}{4}+\dfrac{8019}{4}\)
\(M=\left(\sqrt{x-2005}-\dfrac{1}{2}\right)^2+\dfrac{8019}{4}\ge\dfrac{8019}{4}\)
\(\Rightarrow M_{min}=\dfrac{8019}{4}\) khi \(\sqrt{x-2005}-\dfrac{1}{2}=0\Rightarrow x=\dfrac{8021}{4}\)