Factor completely the expression 4x^5 - 20x^4 - 36x^3.

To simplify the expression, we can check if there are terms that are needed to be added or subtracted. In this case, there are none. We can take out the common terms or numbers among the terms here in this case, 4 and x^3. Hence the factored equation is 4 x^3 (x^2 - 5 x - 9)