Answer:
I believe the answer is D. Hope this helps
Step-by-step explanation:
Let the first term be a(0). Then the formula for a(n) is a(0)-18(n-1).
Check: What's the first term? Let n = 1: a(1) = a(0)-18(1-1) = a(0) (correct)
What's the second term? Let -n =2: a(2) = a(0)-18(2-1) = a(0) - 18
and so on.

get their LCD, like you'd with any other fractions, and add them up