Question

Could someone help, I'm so confused

Answer 1

I will send you a document that I made to help you on this.  It's really hard to explain with words but hopefully the document helps-
1.  Multiply by d and then multiply by -2 until you reach the end
Note- when you do your work you need to add "0 d squared" because you will subtract from it.
The answer is D. 
(I hope that the document sent.)