Answer
$(-\infty,-3]\cup[-2,-1] $.
Work Step by Step
Step 1. For $(x+1)(x+2)(x+3)\le0$, identify boundary points as $x=-3,-2,-1$.
Step 2. Form intervals $(-\infty,-3],[-3,-2],[-2,-1],[-1,\infty)$.
Step 3. Choose test values for each interval $x=-4,-2.5,-1.5,0$.
Step 4. Test the inequality to get results: $True,\ False,\ True,\ False$
Step 5. We have the solution $(-\infty,-3]\cup[-2,-1] $.
