I'm stuck with a differential equation

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Discussion Overview

The discussion revolves around a differential equation of the form ((Ax+B)^4)y''''+ ((Ax+B)^2)y''+(i/const.)y=0, where A, B, and const are constants, and i represents the imaginary unit. Participants are exploring methods to solve this equation, discussing its classification, and addressing the treatment of the complex term i/const.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant requests assistance with a differential equation and seeks possible methods for solving it.
  • Another participant suggests a change of variable to transform the equation into an "Euler-type equation" and proposes a solution form y(t)=t^z, leading to an algebraic equation for z.
  • A participant expresses gratitude for the assistance provided.
  • There is a request for clarification on "Euler Type Equations" and references for further reading.
  • A link to a resource on Euler-type equations is shared as a reference.
  • A participant questions whether the term i/const. can be treated as a constant and expresses confusion regarding its interpretation.
  • Another participant confirms treating i/const. as a constant but notes that its real meaning is context-dependent on the physical problem.
  • A participant provides context about the physical problem involving a planar wave in a medium with a tapered cross-section, questioning how this relates to the treatment of i/const.

Areas of Agreement / Disagreement

Participants have differing views on the treatment of the term i/const., with some considering it a constant while others express uncertainty about its implications in the physical context.

Contextual Notes

The discussion includes assumptions about the nature of the constants and the physical context of the problem, which may influence interpretations and solutions. The treatment of the complex term i/const. remains unresolved.

vinodjoshi
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Please Help ...... Urgent

Hello ppl
I stuck with a differential equation and all I need is your kind help. While solving a problem I got one eqaution as given below


((Ax+B)^4)y''''+ ((Ax+B)^2)y''+(i/const.)y=0


here A, B, and const are constants

i denotes complex no (iota).

I need your kind help. Please suggest me the possible way to solve this equation.

Thanks in advance
 
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First, change variable

x = (tA-B)/A,

where t is new variable. Your ODE in new variable is

(At)^4y''''+ (At)^2y''+(i/const.)y=0 (2)

this is an "equipotential" equation, also known as an "Euler-type equation".

Then seek solution in form y(t)=t^z. Substitution y(t)=t^z to (2) leads to

t^z(A^4 z^4-6 A^4 z^3+11 A^4 z^2-6 A^4 z+A^2 z^2-A^2 z+(i/const.))=0,

There are four solutuons of algebraic equation (z1,z2,z3,z4)

A^4 z^4-6 A^4 z^3+11 A^4 z^2-6 A^4 z+A^2 z^2-A^2 z+(i/const.)=0,

so the general solution of ode (2) is as follows

y(t)=C1t^z1+...+C4t^z4

where C1...C4 are arbitrary constants.
 


Thanks kosovtsov for your kind help.
 


Sir can you briefly explain about these "Euler Type Equations". Can you give me some references for these equations.
 


Sir
Can we treat i/const. as a constant. I am confused about it. Please help me in this regard. Can you suggest me some book having similar kind of problem. I will be thankful to you.
 


vinodjoshi said:
Can we treat i/const. as a constant.

Yes, I have considered i/const as a constant. But real meaning of it belong exclusively to the physical problem setting. I know nothing on the physical base of your problem.
 


Sir, The physical problem belongs to planer wave where the physical medium which carries this wave have tapered cross section. Can this thing help you or I have to explain the problem in detail. All I want to ask (i/const.) is a complex no. so how can we take it as real no.
 

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