Answer
$[-2,2]$
Work Step by Step
Polynomials have as their domain all real numbers, so the $\textbf{j}$ and $\textbf{k}$ components are defined everywhere. However, $\sqrt{x}$ has as its domain $(0,\infty)$ so $4-t^2>0$, giving $t\in [-2,2]$, so the domain of the $\textbf{i}$ component is $[-2,2]$. Thus, the intersection of all these domains is $[-2,2]$, as desired.
