Question

Use the formula for the sum of the first n terms of a geometric sequence to solve. Find the sum of the first 8 terms of the geometric sequence: -8, -16, -32, -64, -128,

Answer 1

-2040

Explanation:

`S_n=a_1(r^n-1)/(r-1) \qquad\text{for first term $a_1$ and common ratio r}\\\\S_8=-8(2^8-1)/(2-1)=-2040`

The sum of the first 8 terms is -2040.