Does the series converge or diverge? If it converges, what is the sum? Show your work.

∑^∞ n=1 −4(−1/2)^n−1

1 answer

To determine if the series converges, we can rewrite it as:

∑^∞ n=1 -4(-1/2)^(n-1)

This is a geometric series with a common ratio of -1/2 and first term of -4.

The sum of an infinite geometric series is given by:

Sum = a / (1 - r)

where a is the first term and r is the common ratio.

Plugging in the values into the formula:

Sum = -4 / (1 - (-1/2))
Sum = -4 / (3/2)
Sum = -4 * (2/3)
Sum = -8/3

Therefore, the series converges and the sum is -8/3.