What is the sum of a 7-term geometric series if the first term is −11, the last term is −171,875, and the common ratio is −5?

−143231

The general term of a geometric series can be described by the formula:

an=arn−1

where the initial term is a and common ratio r.

Then we find:

So dividing both ends by (1−r) we find:

N∑n=1an=a(1−rN)1−r

In our example, N=7, a=−11 and r=−5

So:

number one is the correct answer

step-by-step explanation: dogs and cats are mentioned, no other animals

just do 5.2 + 2 ( 7.2) and 1/3 x 3 (.9) and youv'e got your equation. 0.9( 9/10) + 7.2 ^2 = 16.4 hope i could !

step-by-step explanation: