Find the domain of the function f given by `f(x)=1/(sqrt([x]^2-[x]-6))`

Explanation

For this function, `[x]^2-[x]-6>0`

`=> ([x]-3)([x]+2)>0`

`=> [x] in (-oo, -2) cup (3, oo)`

`=> x in (-oo, -2) cup (4, oo)`