Умножаем на [m] (\sqrt{x+2}+\sqrt{2}) [/m] и числитель и знаменатель:
[m]=lim_{x→ 0}\frac{(\sqrt{x+2}-\sqrt{2})\cdot (\sqrt{x+2}+\sqrt{2})}{x\cdot (\sqrt{x+2}+\sqrt{2})}=lim_{x→0 }\frac{(\sqrt{x+2})^2-(\sqrt{2})^2}{x\cdot (\sqrt{x+2}+\sqrt{2})}=lim_{x→0 }\frac{x+2-2}{x\cdot (\sqrt{x+2}+\sqrt{2})}=lim_{x →0} \frac{1}{\sqrt{0+2}+\sqrt{2}}=\frac{1}{2\sqrt{2}}[/m]