# Getting n alone in n!=x and nlgn=x

## Homework Statement

I need to know the greatest n for which n! is greater or equal to x, and the greatest n for which nlgn is greater or equal to x.

## Homework Equations

Can't think of any. Sorry!

## The Attempt at a Solution

For a "normal" function, like, say, lgn or n^2, it would be as easy as inverting the function and getting n on its own, like this:

lgn = x
n = 2^x (where lg is of base 2)

or

n^2 = x
n = sqrt(x).

However, for n!=x and nlgn=x I can't come up with a way to do this. Help!