From: Chip Eastham on
On Jul 15, 8:19 am, "curious george" <bu...(a)bunch.net> wrote:
> "Tim Little" <t...(a)little-possums.net> wrote in message
>
> news:slrni3t4js.jrj.tim(a)soprano.little-possums.net...
>
>
>
> > On 2010-07-14, A. N. Emus <laini...(a)msn.com> wrote:
> > [ To prove:  x^n + y^n = z^n {1} has no integer solutions for n > 2 ...]
> >> By symmetry we can suppose x < y.  Clearly, y < z.
> > [...]
> >>               x^m(x^2) + y^m(y^2) = z^m(z^2),        {2}
> > [...]
> >>          x^m(x^2) + (x^m + a)y^2 = (x^m + b)z^2,     {3}
> >> where a and b must be some positive integers. Clearly, a < b.
> > [...]
> >>            x^m(x^2 + y^2 - z^2) = bz^2 - ay^2.       {4}
>
> >> There are three choices:
>
> >> [1] x^2 + y^2 - z^2 < 0.
> >> [2] x^2 + y^2 - z^2 > 0.
> >> [3] x^2 + y^2 - z^2 = 0.
>
> >> Choices [1] and [2] are not possible, otherwise the left side of {1}
> >> would be either less than or greater than the right side.
>
> > Why?  Your reasoning is certainly incorrect for non-integer solutions
> > to {1}, and you have given no reason to suppose that it holds for
> > integers.
>
> > - Tim
>
> Tim, how about telling the rest of us why you think his "reasoning is
> certainly incorrect". How incorrect is it? 51% or 99.99999%. an
> unsubstantiated answer to an unsubstantiated claim ( according to you ).

It is completely incorrect at the point where
it is claimed that x^n + y^n = z^n for n > 2
necessarily implies x^2 + y^2 = z^2:

> >> Choices [1] and [2] are not possible,
> >> otherwise the left side of {1}
> >> would be either less than or greater
> >> than the right side.

As Tim points out, this is untrue for real
arguments x,y,z > 0, and the OP gives no
explanation for how integrality of x,y,z
might be used to fill the gap.

regards, chip
From: smallfrey on
Here's some FLT trivia related to inequalities. If n>2, [(x^n + y^n)^(1/n) -x]^(1/n) + [(x^n + y^n)^(1/n) -y]^(1/n) > (x+y)^(1/n) where n is a natural number and x and y are positive real numbers. (I had a proof for n=3, but the dog ate it.) Barlow's formulae implied by a first-case solution of Fermat's equation a^p+b^p=c^p are (c^p-b^p)/(c-b)=R^p, (c^p-a^p)/(c-a)=S^p, (a^p+b^p)/(a+b)=T^p, c-b=r^p, c-a=s^p, and a+b=t^p where rR=a, sS=b, tT=c, and gcd(r,R)=gcd(s,S)=gcd(t,T)=1. (All the prime factors of R, S, and T are of the form pk+1.) Then r divides t^p-s^p, s divides t^p-r^p, and t divides r^p+s^p. By the above inequality, r+s>t>r,s and hence each of r, s, and t has a prime factor of the form pk+1. (Since t divides (r+s)*[(r^p+s^p)/(r+s)]and t is greater than r+s, t and (r^p+s^p)/(r+s) must have a common factor.) This is of little consequence unless all the prime factors of r, s, and t are of the form pk+1.