Question 836577
This question I would suggest reposting with a more clearer question. However, I will take stab in the dark and assume the question is: 

{{{root (5, sqrt(81x))}}}

Knowing that {{{root (n,root(a,x))}}} actually can be rewritten as: {{{root 

(n*a,x)}}} 

so {{{root (5,sqrt(81x))}}} is actually {{{root (2*5,81x)}}} or simply 

{{{root(10,81x)}}} which is  ~ {{{1.55 * root (10,x)}}}


Keep in mind that turn text into a math formula is stored here: 

http://www.algebra.com/services/rendering/regression.mpl?f=regression.txt