Factor the polynomial completely.

4x3 – 12x2 + 7x – 21
4x2(x – 3) + 7(x – 3)
Which is the completely factored polynomial?

4x2(x + 4)
3x2(x – 3)
(4x2 – 7)(x + 3)
(4x2 + 7)(x – 3)