SOLUTION: The first term of a geometric sequence is -4 and the common ratio is -3. (a) What is the tenth term of the sequence? (b) What is the sum of the first 10 terms? --For que

Question 1095278: The first term of a geometric sequence is -4 and the common ratio is -3.
(a) What is the tenth term of the sequence?
(b) What is the sum of the first 10 terms?

--For question (a) I got 78,732. How do I find the answer to question (b)?
Answer by ikleyn(52943) (Show Source): You can put this solution on YOUR website!
.

The n-th term of ANY geometric progression with the first term "a" and the common ratio "r" is


 = .


So, in your case   =  = 78732.


Thus your answer is correct.




The sum of the first n-th terms of ANY geometric progression with the first term "a" and the common ratio "r" is


 = .


So, substitute your values and calculate.

On geometric progressions, there are introductory lessons in this site
    - Geometric progressions
    - The proofs of the formulas for geometric progressions
    - Problems on geometric progressions
    - Word problems on geometric progressions

Also, you have this free of charge online textbook in ALGEBRA-II in this site
    - ALGEBRA-II - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Geometric progressions".

Save the link to this textbook together with its description

Free of charge online textbook in ALGEBRA-II
https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson

into your archive and use when it is needed.

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