The domain of the function $\mathrm{f}\left(\mathrm{x}\right)=\frac{1}{\sqrt{{\left[\mathrm{x}\right]}^2-3\left[\mathrm{x}\right]-10}}$ is (where $\left[\text{x}\right]$ denotes the greatest.  integer less than or equal to x)

$\mathrm{f}\left(\mathrm{x}\right)=\frac{1}{\sqrt{{\left[\mathrm{x}\right]}^2-3\left[\mathrm{x}\right]-10}}$ is real if 

${\left[\mathrm{x}\right]}^2-3\left[\mathrm{x}\right]-10>0$

$(\left[\mathrm{x}\right]-5)(\left[\mathrm{x}\right]+2)>0$

$\left[\mathrm{x}\right]<-2\mathrm{or}\left[\mathrm{x}\right]>5$

$\Rightarrow \mathrm{x}<-2\mathrm{or}\mathrm{x}\ge 6$

$(-\mathrm{\infty },-2)\cup [6,\mathrm{\infty })$