Question

What is the sum of the first 5 terms of this geometric series? Use . -4 + 12 + (-36) + ⋯

Answer 1

Answer:

The sum of the first 5 terms is -244

Step-by-step explanation:

To calculate the sum of the geometric series, we need the first term, the common ratio and the number of terms we would like to sum.

The first term here is -4

The common ratio is T2/T1 or T3/T2 = 12/-4 = -3

number of terms n = 5

The formula to use is;

Sn = a(1-r^n)/(1-r)

Plugging these values, we have;

Sn = -4(1-(-3)^5)/(1-(-3))

Sn = -4(1+243)/4 = -1(244) = -244