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Find the sum of the geometric sequence -3,15,-75,375,... when there are 9 terms

User Jamek
by
7.5k points

1 Answer

4 votes

Answer:

-976,563.

Explanation:

The common ratio is 15/-3 = -75/15 = 375/-75 = -5.

Sum of n terms = a1. (r^n - 1) / (r - 1)

so S9 = -3 * ((-5)^9 - 1)) / (-5 - 1)

= -976,563.

User Byte Lab
by
6.6k points