Answer
$(-\infty,-1)\cup[3,\infty)$.
The graph is shown below.
Work Step by Step
The given compound inequality is
$x\geq3$ or $x\lt-1$.
First graph then take the union of the two inequality.
The graph is shown in the image file.
We can write the compound inequality.
$x\geq3$ as $[3,\infty)$ and $x\lt-1$ as $(-\infty,-1)$
The union is
$(-\infty,-1)\cup[3,\infty)$.