Can the general solution for y in Q*y - y^P = Q - 1 be found analytically?

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Discussion Overview

The discussion revolves around the equation Q*y - y^P = Q - 1 and the quest for a general analytical solution for y, particularly focusing on different values of P. The scope includes mathematical reasoning and exploration of closed forms for specific cases.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in solving the equation for a general P, noting that specific values like P = 2 or 0.5 allow for quadratic solutions.
  • Another participant asserts that there is no general solution for arbitrary P, referencing the Abel-Ruffini theorem and suggesting that closed forms exist only for certain integer values and special fractions.
  • A participant inquires about the existence of closed forms specifically for P values between 0 and 1.
  • It is noted that y=1 is a trivial solution, and questions arise about the existence of additional real or complex solutions depending on the value of Q.
  • One participant mentions that for certain fractional values of P, the equation can be transformed into solvable forms like quadratic or cubic equations, but emphasizes the lack of a general closed form.
  • Another participant introduces the concept of Galois groups, suggesting that the solvability of the equation by radicals is contingent on the nature of its Galois group.

Areas of Agreement / Disagreement

Participants generally disagree on the existence of a general solution, with some asserting that closed forms are limited to specific cases while others explore the implications of different P values.

Contextual Notes

Limitations include the dependence on the specific values of P and Q, as well as the unresolved nature of solutions for arbitrary P. The discussion also highlights the complexity introduced by the Galois group in determining solvability.

kairama15
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I am having difficulty solving Q*y - y^P = Q - 1 for y.
If P = 2 or 0.5 or 0, I can solve it quadratically. However, I'd like to find a general solution for y. Any tips?
 
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There is no general solution. If P is an integer from -3 to 4, or a few special fractions, the equation has closed forms for its solutions, but for arbitrary P this is no longer true. Abel-Ruffini theorem.
 
kairama15 said:
I am having difficulty solving Q*y - y^P = Q - 1 for y.
If P = 2 or 0.5 or 0, I can solve it quadratically. However, I'd like to find a general solution for y. Any tips?

Where did you got this question from ?
 
For the particular problem I am trying to solve, P ranges from 0 to 1. Is there a closed form for 0<P<1 ?
 
y=1 is always a trivial solution, of course.
Are there more real solutions in some cases? Are you interested in complex solutions?

For 1/4, 1/3, 1/2, 2/3, 3/4 you can convert it to a quadratic, cubic or quartic equation and solve it. Otherwise there is no closed form for a solution in the general case. There can still be values of Q were you can find all solutions, but it won't work for all Q any more, unless y=1 is the only solution.
 
Isn't the result that a solution by radicals exists iff the Galois group of the equation is solvable? EDIT: I mean, of course for this equation; we can construct equations whose group is not solvable, e.g., ##A_5 ##
 

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