What is the factored form of 4x³ – 24x² – 28x?

The correct answer is: 4x (x – 7) (x + 1)

4x³ – 24x² – 28x
Take out the x and 4 as common, 4x (x² – 6x – 7)
Now, let’s take the quadratic equation of the form ax² + bx + c, which is x² – 6x – 7.
Here we have to factorise middle term, whose sum is -6 and whose product is -7.
(x – 7) (x + 1)
= x² + x – 7x – 7 = x² – 6x – 7