# How do you find nth term rule for #a_2=5# and #a_4=1/5#?

##### 1 Answer

Aug 16, 2016

There are two possibilities:

#a_n = 25(1/5)^(n-1)#

#a_n = -25(-1/5)^(n-1)#

#### Explanation:

Assuming that this is a geomtric sequence, since that's the topic under which it is posted...

The general formula for the

#a_n = ar^(n-1)#

where

In our example, we find:

#r^2 = (ar^3)/(ar^1) = a_4/a_2 = (1/5)/5 = 1/25#

Hence

If

If