Answer
$ (4,\infty)$
Work Step by Step
Step 1. Factor and identify boundary points (zeros) $x^2(x-4)\gt0$ as $x=0,4$ which divide the x-axis into three intervals $(-\infty,0),(0,4),(4,\infty)$
Step 2. Choose test values in each interval $x=-1,1,5$ and test the inequality to get $False,\ False, \ True$
Step 3. Thus the solution interval is $ (4,\infty)$