Find the eigenvalues of this endomorphism of R[X]

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Homework Help Overview

The problem involves finding the eigenvalues of an endomorphism of the polynomial space R[X], defined by the operation f(P)(X) = ((aX+b)P)'. The parameters a and b are specified to be non-zero.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to analyze the case when a=0 and a≠0, exploring the implications for the eigenvalues. There is a discussion about the correct formulation of the function f(P) and the resulting equations derived from it.

Discussion Status

Participants are actively clarifying the definition of the endomorphism and correcting each other's interpretations. One participant has provided guidance on the relationship between the variables involved, leading to a clearer understanding of the conditions for c.

Contextual Notes

There is an emphasis on ensuring that the resulting polynomial P remains valid, specifically that c/a - 1 must be an integer. The discussion reflects on the constraints imposed by the definitions and the nature of polynomial functions.

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Homework Statement



f is an endomorphism of Rn[X]
f(P)(X)=((aX+b)P)'

eigenvalues of f?

Homework Equations



(a,b)<>(0,0)

The Attempt at a Solution



If a=0, then f(P)=bP', and only P=constant is solution

if a<>0, then I put Q=(ax+b)P, f(P)=cP is equivalent to (ax+b)Q'=Q (E)

I solved (E) and found Q(X)=(aX+b)^c but then if I say P(X)=(aX+b)^(c-1), I can't find c...
 
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Is f(P)=(aX+b)P' or [(aX+b)P]'? You wrote it both ways.
 


f(P)=[(aX+b)P]'
 


Sorry, I misread your initial post. I see what you did now. Your solution for Q(X) should be [itex]Q(X)=(aX+b)^{c/a}[/itex] so [itex]P(X)=(aX+b)^{c/a-1}[/itex]. Do you see now what values c can be?
 


Thanks a lot vela, I mistook when I solved (E)... Now I can see the values for c (s.t c/a-1 is integer and therefore P is a polynom)...
 

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