Question

Find the sum of the first 9 terms of the following sequence. Round to the nearest hundredth if necessary.

3,-15,75

Sum of a finite geometric series:
Sn=a1-a1r^n/1-r

Answer 1

The given sequence is not a geometric sequence since there is no common ratio between the terms. However, we can still find the sum of the first 9 terms by adding them individually.

First term, a1 = 3

Second term, a2 = -15

Third term, a3 = 75

Sum of the first 9 terms:

3 + (-15) + 75 + 3 + (-15) + 75 + 3 + (-15) + 75

= 204

Therefore, the sum of the first 9 terms of the given sequence is 204.