Is There a General Solution to This Second-Order ODE?

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Discussion Overview

The discussion revolves around the existence of a general solution for the second-order ordinary differential equation (ODE) given by the expression \(\frac{d}{dt}\left[p(t)\frac{dx(t)}{dt}\right] + q(t)x(t) = 0\), where \(p(t)\) and \(q(t)\) are arbitrary functions. Participants explore the nature of the solutions, potential methods for solving the equation, and related concepts.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant questions whether there is a general solution for the ODE and seeks further identification of the problem.
  • Another participant asserts that there is no general solution, implying that a closed-form analytical solution does not exist.
  • A different participant suggests looking into Sturm-Liouville problems as a related concept that may provide insight.
  • One participant expands on the nature of the ODE, indicating it involves non-constant coefficients and proposes that power series might be a viable method for certain forms of \(p(t)\) and \(q(t)\).
  • A later reply clarifies that the statement about the absence of a general solution refers specifically to the lack of a general analytical solution in closed form, while acknowledging that particular cases may yield known solutions or that numerical methods can provide approximations.

Areas of Agreement / Disagreement

Participants express differing views on the existence of a general solution, with some asserting that no general analytical solution exists while others suggest that specific cases may allow for known solutions. The discussion remains unresolved regarding the generality of solutions for arbitrary functions.

Contextual Notes

Participants note that the nature of the functions \(p(t)\) and \(q(t)\) significantly influences the solvability of the ODE, and that the discussion does not reach a consensus on the existence of solutions under all conditions.

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Is there a general solution to

[tex]\frac{d}{dt}\left[p(t)\frac{dx(t)}{dt}\right] + q(t)x(t) = 0[/tex]

for [itex]x(t)[/itex] when [itex]p(t)[/itex] and [itex]q(t)[/itex] are arbitrary functions? Better yet, does this question have a name, or some identifier, that I could look in to? It might appear more familiar written as

[tex]\left[p(t)x^\prime\right]^\prime + q(t)x = 0[/tex]
 
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Undoubtedly0 said:
Is there a general solution to
[tex]\frac{d}{dt}\left[p(t)\frac{dx(t)}{dt}\right] + q(t)x(t) = 0[/tex]
for [itex]x(t)[/itex] when [itex]p(t)[/itex] and [itex]q(t)[/itex] are arbitrary functions?

No, there is no genertal solution
.
 

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Undoubtedly0 said:
Is there a general solution to

[tex]\frac{d}{dt}\left[p(t)\frac{dx(t)}{dt}\right] + q(t)x(t) = 0[/tex]

for [itex]x(t)[/itex] when [itex]p(t)[/itex] and [itex]q(t)[/itex] are arbitrary functions? Better yet, does this question have a name, or some identifier, that I could look in to? It might appear more familiar written as

[tex]\left[p(t)x^\prime\right]^\prime + q(t)x = 0[/tex]

Look up Sturm-Liouville problems or equations.
 
I think that's just a ODE with non constant coeffecients, since expanding yields

P(t)x''+P'(t)x'+q(t)x=0

You may be able to solve this with power series if P and q fit them.
Non linear differential equations rarely have closed form solutions.
But that's okay, we have computers
 
Of course, when I say "There is no general solution", I mean "No general analytical solution espressed on a closed form".
Obviously, in some particular cases, with some particular forms of functions p(t) and q(t), the solutions might be known on closed form, and/or be expressed as infinite series.
Even more generally the solutions can be accurately approached thanks to numerical methods.
 

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