## anonymous 3 years ago Write the explicit formula for the geometric sequence. -5, 20, 80

1. anonymous

Did you mean - 80? That's not a geometric sequence unless the 80 is negative.

2. anonymous

yes

3. anonymous

can you help me?

4. anonymous

I have an answer, but I'm \not sure how \to explain how I got it.LOL

5. anonymous

$a _{n}=-5\times(-4)^{(n-1)}$

6. anonymous

Plug in n=1 and you get -5, plug in n=2 and you get 20, plug in ....etc

7. anonymous

i understand now how to do it now thanks