# How do you find these missing terms [__,8,__,128,....]?

##### 1 Answer

Jun 6, 2016

There are two solutions:

#4# and#32#

Or:

#-4# and#-32#

#### Explanation:

If the general term of the sequence is

A geometric sequence has

The general term of a geometric sequence is described by the formula:

#a_n = a*r^(n-1)#

where

In our example, we find:

#r^2 = (a r^3)/(a r) = a_4/a_2 = 128/8 = 16 = 4^2#

So

If

#a_1 = a_2/r = 8/4 = 2# and#a_3 = a_2*r = 8*4 = 32#

If

#a_1 = a_2/r = 8/(-4) = -2# and#a_3 = a_2*r = 8*(-4) = -32#