M= \(\dfrac{\sqrt{x}-2}{\sqrt{x}+1}\)
M= \(1-\dfrac{3}{\sqrt{x}+1}\)
M= \(1+\dfrac{3}{\sqrt{x}-1}\)
Để M min  <=> \(\dfrac{3}{\sqrt{x}-1}min\)
<=> \(\left\{{}\begin{matrix}\sqrt{x}-1< 0\\\sqrt{x}-1max\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x< 1\\xmax\end{matrix}\right.,x\in N\)
=> x=0 ( t/m )
Thay x=0 vào M có:
M= \(\dfrac{\sqrt{0}-2}{\sqrt{0}+1}=-2\)
Vậy Mmin = -2 <=> x=0