Question

Find the sum of the first 8 terms in the geometric sequence: 1, 3, 9, 27,

Answer 1

The sum of the first 8 items in the geometric sequence:1, 3, 9, 27, ...etc is 3280.

Step-by-step explanation:

The given is,

            sequence: 1,3,9,21,.. etc

Step:1

           The given is based on multiplication of 3 to previous number,

           ( x - previous number, next number = 3 × $x$ )

            First term : 1

            Second term : 1 × 3 = 3

           Third term : 3 × 3 = 9

            Fourth term : 9 × 3 =27

            Fifth term : 27 × 3 = 81

            Sixth term : 81 × 3 = 243

            Seventh term : 243 × 3 = 729

            Eighth term : 729 × 3 = 2187

Step:2

            Sum of first 8 terms $= 1 + 3 + 9 + 27 + 81 + 243 + 729 + 2187$

                                              = 3280

            Sum of first 8 terms = 3280

Result:

           The sum of the first 8 items in the geometric sequence:1, 3, 9, 27, ...etc is 3280.