don't let the negatives bother you, just grind though. the negative in front of the d on the top is not being squared, so you can bring that out to the front. the one in front of the d at the bottom is being squared, so it will go away (that is, d^2 = (-d)^2), so you can pretty much forget about that one. otherwise, you need to know:

so you could write:

where means multiply.

Now continue