From: blang on
Hi :)

Let P and Q in IR[X] (with deg(P)>0 and deg(Q)>0) such that : for all n in IN*, P^n-1|Q^n-1.
Is it true that we can find k in IN* such that Q=P^k ?

Thanks !
From: William Elliot on
On Tue, 29 Jun 2010, blang wrote:

> Let P and Q in IR[X] (with deg(P)>0 and deg(Q)>0) such that : for all n
> in IN*, P^n-1|Q^n-1.

Do you mean
p^(n-1) | q^(n-1)
or
(p^n - 1) | (q^n - 1) ?

> Is it true that we can find k in IN* such that Q=P^k ?
>
No or I don't know.
From: blang on
(P^n-1) | (Q^n-1) , of course !

>Do you mean
>p^(n-1) | q^(n-1)
>or
>(p^n - 1) | (q^n - 1) ?
From: achille on
On Jun 30, 2:32 pm, blang <bl...(a)laposte.net> wrote:
> (P^n-1) | (Q^n-1) , of course !
>
> >Do you mean
> >p^(n-1) | q^(n-1)
> >or
> >(p^n - 1) | (q^n - 1) ?

It is true for the special case p(z) = z.

When p(z) = z, the condition p^n - 1 | q^n - 1 for all n
=> |q(z)| = 1 for any complex z satisfies |z| = 1.
Since p \in R(z), this implies on the unit circle,
q(z) q(1/z) = q(z)q(z*) = q(z)(q(z))* = |q(z)|^2 = 1.
It is then easy to check q(z) must has the form z^k.

No idea about the general case :-(
From: William Elliot on
On Wed, 30 Jun 2010, blang wrote:

> (P^n-1) | (Q^n-1) , of course !
>
What happen to the problem statement?
With it being removed from your reply,
there's nothing to comment other than does
p^n-1 mean p^(n-1) or p^n - 1, ie (p^n) - 1?

>> Do you mean
>> p^(n-1) | q^(n-1)
>> or
>> (p^n - 1) | (q^n - 1) ?

Please include essential content _within_ your reply
http://oakroadsystems.com/genl/unice.htm

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