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5.6.2 The Sum of the First n Terms of a Geometric Progression


Instructions: Use the following tutorial to help introduce or reinforce the concept of the Sum of the First n Terms of a Geometric Progression. Read through the introduction, then study and familiarize yourself with the definitions of terms. Next, use the incremental calculator to study each step of the process of the Sum of the First n Terms of a Geometric Progression. Finally, use the calculator for examples to quiz yourself.
An geometric progression is a sequence or pattern of numbers in which each term is calculated by multiplying r to the previous number. The sum Sn of first n terms of a geometric progression is obtained by using first term a and the common ratio r
Sn= a[(1 - rn) /(1 - r)]
for r not equal to 1
Sn= (n)(a)
when r =1
An example of this problem is to find the sum of the first ten terms of the sequence 2,4,8,16....
a= 2, n= 10, and r= 2, Sn=2(1- 210)/(1 - 2)= 2046. Thus the sum of the first ten terms term 1024.

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