Does the equation x^x^x^x^x^...=n hold true for all numbers?

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Discussion Overview

The discussion revolves around the equation x^x^x^x^x^...=n and whether it holds true for all numbers. Participants explore the conditions under which this equation is valid, particularly focusing on the range of n between 1/e and e, and the implications of the Lambert W-function in this context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that the equation x^x^x^x^...=n leads to x=n^(1/n) but only holds true for 1/e ≤ n ≤ e.
  • Others question the reasoning behind the restriction of n to the interval [1/e, e], seeking clarification on why this range is significant.
  • One participant mentions that for n=2, the equation simplifies to x=2^(1/2), raising the question of whether the equation is valid for any number.
  • Another participant introduces the Lambert W-function, suggesting that the real values of the function are only valid for x ≥ -1/e, which may relate to the conditions discussed.
  • Some participants note that as n moves away from 1, the convergence of the iterative process slows down, indicating that for n outside the specified range, the equation may not approach n effectively.
  • There is a mention of exploring logarithmic iterations, specifically the equation log_x(log_x(log_x(...)))=2, which leads to x^2=2, indicating a potential connection to the original discussion.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the conditions under which the equation holds true, with multiple competing views on the significance of the range for n. The discussion remains unresolved as participants continue to seek clarification and explore different mathematical perspectives.

Contextual Notes

Limitations include the dependence on the properties of the Lambert W-function and the assumptions regarding convergence rates for values of n outside the specified range.

MAGNIBORO
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hi, sorry for bad english,
watching videos on youtube I found this video:


and ask me if that equation works for any number and comes to the conclusion that

x^x^x^x^x^...=n
x=n^(1/n)

but this only works if the number is 1/e ≤ n ≤ e
and I wonder if this is a property of e or happens if for some other reason.
thak you
 
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MAGNIBORO said:
but this only works if the number is 1/e ≤ n ≤ e

Why? I don't see it.
 
axmls said:
Why? I don't see it.
The video says that
x^x^x^x^...=2
x= 2^(1/2)

then I wanted to know if it works for any number.

example: x^x^x^x^...=1.5
x=1.5^(1/1.5)

x^x^x^x^...=n
x=n^(1/n)

but using my calculator , I realized that this only works if 1/e ≤ n ≤ e

and I would like to know why this happens
 
##z^{z^{z..}} = \frac{W(-\log z)}{-\log(z)}## for complex z, where we have used Lambert W-function and the principal branch of the logarithm. The W function is real valued only for ##x \geq -1/e##. I'm assuming it has something to do with that.
 
MAGNIBORO said:
x^x^x^x^x^...=n
x=n^(1/n)

but this only works if the number is 1/e ≤ n ≤ e
and I wonder if this is a property of e or happens if for some other reason.
x^x^x^x = x^(x^(x^x))

At each step (when you add more x = n^(1/n)) the calculation approaches it's destination slower and slower.

The further away n is from 1 the slower the calculation approaches it's destination. If n is less than 1/e or more than e, the calculation approaches it's
destination so slow and still slowing that you can't say it's approaching n.

This is a property of n^(1/n). It has it's maximum at n = e.
 
pwsnafu said:
##z^{z^{z..}} = \frac{W(-\log z)}{-\log(z)}## for complex z, where we have used Lambert W-function and the principal branch of the logarithm. The W function is real valued only for ##x \geq -1/e##. I'm assuming it has something to do with that.

Thanks for your input , and sorry for late response
 
forcefield said:
x^x^x^x = x^(x^(x^x))

At each step (when you add more x = n^(1/n)) the calculation approaches it's destination slower and slower.

The further away n is from 1 the slower the calculation approaches it's destination. If n is less than 1/e or more than e, the calculation approaches it's
destination so slow and still slowing that you can't say it's approaching n.

This is a property of n^(1/n). It has it's maximum at n = e.
thanks and sorry for late answer
 
Now we can try to solve

## \log_{x}{(\log_{x}{(\log_{x}(...))})}=2 ##

so ## x^{2}=2##, huao is the same ... :- D
 

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