Answer
$ (-8,2) $
Work Step by Step
Step 1. $x^2+6x-16\lt0 \Longrightarrow (x+8)(x-2)\lt0$
Step 2. Identify boundary points $x=-8,2$ and form intervals $(-\infty,-8),(-8,2),(2,\infty)$
Step 3. Choose test values $x=-9,0,3$, test the inequality to get results $False,\ True,\ False$.
Step 4. Thus we have the solution $ (-8,2) $
