Question

Please help ASAP; it is based off of sequences

Answer 1

`a_n= - 1( - 2)^(n-1)`

Explanation:

The given geometric sequence is :

-1,2,-4,8,...

The first term is

`a_1=-1`

The common ratio is

`r = (2)/( - 1) = - 2`

The nth term is given by;

`a_n=a_1(r^(n-1))`

We substitute the values of the first term and common ratio to get:

`a_n= - 1( - 2)^(n-1)`

This is called the explicit formula.