Find the sum of the first 9 terms in the following geometric series.
do not round your answer.
7+21 +63 +

The sum of first 9 terms of the given sequence = 68887

Step-by-step explanation:

Given sequence:

7+21+63......

The given sequence is a geometric sequence as the successive numbers bear a common ratio.

The ratio can be found out by dividing a number by the number preceding it.

For the given geometric sequence common ratio can be given as:

The sum of a geometric sequence is given by:

      when

and

     when

where, represents sum of terms, representing number of terms and represents common ratio and represents the first term.

Since for the given geometric sequence has a common ratio =3 which is >1, so we will use the first formula for sum to calculate the sum of first 9 terms.

Plugging in the values to find sum of first 9 terms.

∴  

Thus sum of first 9 terms of the given sequence = 68887 (Answer)

step-by-step explanation:

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