Answer
$ (4,\infty)$.
Work Step by Step
Step 1. For $x^3-4x^2\gt0 \Longrightarrow x^2(x-4)\gt0$, identify boundary points as $x=0,4$.
Step 2. Form intervals $(-\infty,0),(0,4),(4,\infty)$.
Step 3. Choose test values for each interval $x=-1,1,5$.
Step 4. Test the inequality to get results: $False,\ False,\ True$
Step 5. We have the solution $ (4,\infty)$.
