SOLUTION: Hello I really need help. PLEASE HELP ME... Use the geometric sequence of numbers 1, 3, 9, 27, … to find the following: a) What is r, the ratio between 2 consecutive terms

Algebra ->  Sequences-and-series -> SOLUTION: Hello I really need help. PLEASE HELP ME... Use the geometric sequence of numbers 1, 3, 9, 27, … to find the following: a) What is r, the ratio between 2 consecutive terms      Log On


   



Question 84239: Hello I really need help. PLEASE HELP ME...

Use the geometric sequence of numbers 1, 3, 9, 27, … to find the following:
a) What is r, the ratio between 2 consecutive terms?
Show work in this space.



b) Using the formula for the nth term of a geometric sequence, what is the 10th term?
Show work in this space.



c) Using the formula for the sum of a geometric sequence, what is the sum of the first 10 terms?
Show work in this space.

Answer by vertciel(183) About Me  (Show Source):
You can put this solution on YOUR website!
Use the geometric sequence of numbers 1, 3, 9, 27, … to find the following:
a) What is r, the ratio between 2 consecutive terms?
Show work in this space.
To find the ratio, just compare each two consecutive terms.
Compare 1:3, 3:9, 9:27, do you see how the second integer is related to the first in terms of multiplication?

b) Using the formula for the nth term of a geometric sequence, what is the 10th term?
Show work in this space.
To calculate the nth term of a geometric sequence, the formula is an = (a1)(r^n-1). I assume your textbook has this.
Substitute your values and you should get an = 3^(n-1). Try it from here.


c) Using the formula for the sum of a geometric sequence, what is the sum of the first 10 terms?
Show work in this space.
The formula of for the sum of a finite geometric sequence is sn = (a1 x (1 - r^n))/1 - r
Substitute the values and you will have your answer.