Question

Please help ASAP; it is based off of sequences

Answer 1

Answer:

$a_n= - 1( - 2)^{n-1}$

Step-by-step explanation:

The given geometric sequence is :

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

The first term is

$a_1=-1$

The common ratio is

$r = \frac{2}{ - 1} = - 2$

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.