174k views
4 votes
Select the best answer for the question.

2. Find the sum of the first 8 terms of a geometric series in which a1 = 3 and r= 2.​

2 Answers

6 votes

Answer: Answer: 765

Work Shown:

a = 3 is the first term

r = 2 is the common ratio

Sn = a*(1-r^n)/(1-r) ... sum of the first n terms

S8 = 3*(1-2^8)/(1-2) ... sum of the first 8 terms

S8 = 3*(-255)/(-1)

S8 = 765

User Martin Lottering
by
7.7k points
2 votes

Answer: 765

=============================================

Work Shown:

a = 3 is the first term

r = 2 is the common ratio

Sn = a*(1-r^n)/(1-r) ... sum of the first n terms

S8 = 3*(1-2^8)/(1-2) ... sum of the first 8 terms

S8 = 3*(-255)/(-1)

S8 = 765

----------

We can generate the first 8 terms to get 3, 6, 12, 24, 48, 96, 192, 384. Each new term is found by multiplying the previous one by 2.

Then add them up to get 3+6+12+24+48+96+192+384 = 765. We get the same result.

User Moustapha
by
9.1k points

No related questions found

Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.

9.4m questions

12.2m answers

Categories