Find the sum of the first 9 terms of the geometric series: 3 + 21 + 147 + …

Mathematics

1 answer:

grin007 [14]3 years ago

8 0

Answer:

20,176,803

Step-by-step explanation:

This geometric series has a first term of 3 and a common ratio of 21/3 = 7. The formula for the sum of n terms of a series with first term a1 and common ratio r is ...

Sn = a1·(r^n -1)/(r -1)

For a1=3, n=9, and r=7, the sum is ...

S9 = 3·(7^9 -1)/(7 -1) = 3·40353606/6 = 20,176,803

The sum of the first 9 terms is 20,176,803.

_____

The first 9 terms are ...

3 +21 +147 +1029 +7203 +

50,421 +352,947 +2,470,629 +17,294,403

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koban [17]

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