Answer
$(-\infty,-1]U[4,\infty)$
Work Step by Step
Step 1. The domain requirements of the function is $x^2-3x-4\ge0$ or $(x+1)(x-4)\ge0$
Step 2. The boundary points are $x=-1, 4$ which forms intervals $(-\infty,-1],[-1,4],[4,\infty)$
Step 3. Choose test values $x=-2,0,5$ and test the inequality to get $True,\ False,\ True$
Step 4. Thus the solution intervals are $(-\infty,-1]U[4,\infty)$
