Question

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

Answer 1

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

Explanation:

The formula:

`S_n=(a_1(1-r^n))/(1-r)`

Substitute:

`n=8;\ r=3;\ a_1=1\\\\S_8=(1\cdot(1-3^8))/(1-3)=(1-6,561)/(-2)=(6,560)/(2)=3,280`