
By calculation,
radical n to the radical (n+1) <
radical (n+1) to the radical n
for n = 1 through 6, and
radical n to the radical (n+1) >
radical (n+1) to the radical n
for n= 7 and 8.
What happens as n gets larger?
Algebraic manipulation tells us that the question as posed
is equivalent to asking whether
[radical (n+1)]ln
n <>? (radical n) ln (n+1)
Consider the expression (radical n) (ln
n). Our problem is equivalent to asking whether this expression will grow
faster if we increase the number under the radical by 1 or increase the number
under the natural log by 1. Rate of growth is equivalent to slope: that
is, the derivative.
The derivative of radical n is 1/ 2radicaln, while the
derivative of ln n is 1/n. For n =5 or more,
1/2radicaln is greater than 1/n. As a result, for n sufficiently large,
the slope is greater when we increase the radicaln
expression by 1 than when we increase the ln
expression by 1. SO, for all n >=7,
radical n to the radical (n+1) >
radical (n+1) to the radical n
Dave Stone