Answer:
32
Step-by-step explanation:
The formula needed to solve this question by hand is:
![x^{\frac{m}{n}} =\sqrt[n]{x^{m}}](https://tex.z-dn.net/?f=x%5E%7B%5Cfrac%7Bm%7D%7Bn%7D%7D%20%3D%5Csqrt%5Bn%5D%7Bx%5E%7Bm%7D%7D)
256^(5/8) = 8th root of 256^5
256^(5/8) = 8th root of 1280
<u>256^(5/8) = 32</u>
The rule of a geometric sequence:

We have:

Find 
substitute:

Answer:
So do you already have the answer? Also 1/20 looks right.
Step-by-step explanation:
(x² + 16)(x² - 16)
= (x²)² - 16²
= x⁴ - 256