Question

what is the sum of a 7 term geometric sequence if the first term is -6 the last term is -24,567 and the common ratio is -4?

Answer 1

Answer:

Sum = -19662

Step-by-step explanation:

first term is -6

the last term is -24,567

and the common ratio is -4

Sum of geometric series formula is

$S_n = \frac{a_1(1-r^n)}{1-r}$

a1 is the first term = -6

r is the common ratio = -4

n is the number of terms = 7

Plug in all the values in the formula

$S_n = \frac{-6(1-(-4)^7)}{1-(-4)}$

$S_7 = \frac{-6(1 + 16384)}{5}= -19662$

Sum = -19662