Answer
$x\gt4$.
Work Step by Step
We know that $(x-k)^2\geq0$ for all $k$.
$x^3-4x^2=x^2(x-4)$
So here for the inequality to be true, $x-4\gt0\\x\gt4$ and $x^2\ne0\\x\ne0$
So the solution is $x\gt4$.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.