Use the formula for the n-th term of geometric progression

 = .

With the given data, you have 

 =   --->   =  = 256  --->   = .

This fourth root has 4 values in the complex domain, but if you need only real values, they are +/- 4.

The formula for a specific term in a GP is: , where:

 is the value of the term 

 is the value of the 1st term

    is the term number



For the 5th term,  becomes: 











 

RELATED QUESTIONS

The first term of a geometric progression is 5 and the fifth term is 1280, the common... (answered by ikleyn)

The first term of a geometric progression is 5 and the fifth term is 1280, the common... (answered by ikleyn,MathTherapy)

The first term of a geometric progression is 5 and the fifth term is 1280, the common... (answered by stanbon)

the first term of a geometric progression is 5 and the fifth term is 1280 and the common... (answered by ikleyn)

The first term of an arithmetic progression is 12 and the sum of the first 16 terms is... (answered by greenestamps)

A geometric progression and an arithmetic progression have the same first term. The... (answered by htmentor)

The nth term of a geometric progression is 9(-2/3)^n. Find the first term and the common
 (answered by ikleyn)

The fifth term of a geometric progression is 1 and the common ratio is ½. Find the eight  (answered by ikleyn)

The 2nd, 4th and 8th terms of an arithmetic progression are the three consecutive terms... (answered by mananth)