$\lim_{x\to 0} {[\sqrt{2} x]\over x}=\sqrt{2}-\lim_{x\to 0}{\{\sqrt{2} x\}\over x}$
Now $\lim_{x\to 0}{\{\sqrt{2} x\}\over x}=0$, how will I make understand to my school students who do not know the epsilon delta definition of limit.
$\lim_{x\to 0} {[\sqrt{2} x]\over x}=\sqrt{2}-\lim_{x\to 0}{\{\sqrt{2} x\}\over x}$
Now $\lim_{x\to 0}{\{\sqrt{2} x\}\over x}=0$, how will I make understand to my school students who do not know the epsilon delta definition of limit.
If $[x]$ is the floor function and $\{x\} = x - [x]$ then I think you are wrong. In fact $[\sqrt 2 x]=0$ if $x \to 0^+$ while $[\sqrt 2 x] = -1$ if $x\to 0^-$ hence the given limit does not exist.