Question

Enter a recursive rule for the geometric sequence. 6, −18, 54, −162, ...

Answer 1

Answer:

The required recursive formula is:

$a_n=(-3)\times a_{n-1}$

Step-by-step explanation:

We are given a geometric sequence as:

6,-18,54,-162,.....

Clearly after looking at different terms of the sequence we could observe that the sequence is an geometric progression (G.P.) with common ratio= -3 denoted by r.

Let $a_n$ represents the nth term of the sequence.

This means that:

$a_1=6, a_2=-18, a_3=54, a_4=-162,......$

As the common ratio is -3.

so,

$a_1=6\\\\a_2=-18=(-3)\times a_1\\\\a_3=54=(-3)\times a_2\\\\.\\.\\.\\.\\.\\.\\.\\.\\.a_n=(-3)\times a_{n-1}$

Hence, the required recursive formula for the geometric sequence is:

$a_n=(-3)\times a_{n-1}$