convert fractional power to radical

[webmasterpdx]

There is a way to do this in a program. You'd have to write a function as follows...
Convert the expression to a string. Then, wherever NTHROOT shows up in the string, substitute for dd NTHROOT x with x^(1/dd). Likewise, to go the other direction, search for x^(1/dd) and convert to dd NTHROOT x, still in string format.
Then call EXPR on the result.
Enjoy. Publish this if you write it :-)