Find the sum of the geometric sequence −3, 15, −75, 375, when there are 7 terms and select the correct answer below. −39,063 39,063 58,593 −58,593

ANSWER

−39,063

EXPLANATION

The given geometric sequence is

-3,15,-75,375,...

The sum of the first n-terms of a geometric sequence is calculated using the formula;

Where a=-3 is the first term of the geometric sequence and

is the common ratio of the sequence.

The sum of the first seven terms is

This simplifies to:

5

10

15

20

25

30

35

40

45

50

55