What is - 4d 3 + 28d 2 - 4d

Answer: 20d + 5

Step-by-step explanation:

First we need to combine like terms.

In this equation we can see that they're are 3 numbers containing the letter D we have - 4, - 4, 28.

We're going to combine - 4 and - 4 to get - 8 and then combine - 8 to 28 getting 20d

Afterwards we're going to combine 3, 2 equaling 5.