Question

Find the sum of the first five terms using the geometric series formula for the sequence 1/2, -1,2,-4…

Answer 1

The sum of the first five terms is 11/2

How to determine the sum?

The series is given as:

1/2, -1,2,-4…

Calculate the common ratio of the series using

r = -4/2

Evaluate

r = -2

The sum is then calculated as:

$S_n = a\frac{1 - r^n}{1 - r}$

This gives

$S_n = \frac{1}{2} * \frac{(1 - (-2)^5}{1 + 2}$

Evaluate

$S_n = \frac{1}{2} * \frac{33)}{3}$

Evaluate

$S_n =\frac{11}{2}$

Hence, the sum of the first five terms is 11/2

Read more about series at:

brainly.com/question/11346378

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