Question

Find the sum of the geometric series if: n = 8, r = 3, a = 1.​

Answer 1

Answer:

$\huge\boxed{S_8=3,280}$

Step-by-step explanation:

The formula:

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

Substitute:

$n=8;\ r=3;\ a_1=1\\\\S_8=\dfrac{1\cdot(1-3^8)}{1-3}=\dfrac{1-6,561}{-2}=\dfrac{6,560}{2}=3,280$