Higher order differential equation

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Homework Help Overview

The discussion revolves around solving a higher order differential equation given by the initial value problem: 2007y(4)-18y(3)+178y(1) = 0, with initial conditions y(0)=y(1)(0)=y(2)(0)=y(3)(0). Participants express confusion regarding the nature of the roots and the implications of the initial conditions.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the difficulty in finding the roots of the characteristic equation derived from the differential equation. There is uncertainty about whether an explicit solution is required and how to interpret the initial conditions. Some participants explore the nature of the roots, questioning if they are complex, repeating, or real and distinct.

Discussion Status

The discussion is active, with participants sharing their attempts to analyze the roots of the equation. Some guidance has been offered regarding the implications of the initial conditions, noting that one arbitrary constant will be present in the solution. Multiple interpretations of the problem are being explored, particularly concerning the roots of the characteristic polynomial.

Contextual Notes

Participants note the lack of specific values for the initial conditions, which are stated to be equal to each other, leading to confusion about the expected form of the solution. There is also mention of the complexity involved in solving the characteristic equation.

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Homework Statement



Solve the following initial value problem:

2007y(4)-18y(3)+178y(1) = 0

with initial conditions y(0)=y(1)(0)=y(2)(0)=y(3)(0)

Homework Equations



Differential equations..

The Attempt at a Solution



From the equation I get r(2007r3 - 18r2 +178) = 0

Well first I can't seem to find the roots of the equation (except for r=0) with any method I've been taught and also the fact that they don't actually give any values for the initial conditions but just states that they're equal to each other confuses me. I figure they are just asking for the general solution but I just need to find the roots of the equation which I can't seem to do.
 
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Do you need an explicit exact solutuion?
r(2007r3 - 18r2 +178) = 0
is messy to solve

Since you have
y(0)=y(1)(0)=y(2)(0)=y(3)(0)
You will have one arbitrary constant in your solution.
 
They are not asking to find an exact solution but to just find y(t). I suppose if I could just find out if there's someway to tell if the roots are complex,repeating or just real and distinct I could write out the forumlas for each.
 
The roots are approximately
{0,.225977+.386191j,.225977-.386191j,-.442985}
where j^2=-1
The zero root is obvious.
(2007r3 - 18r2 +178)
is optimal when the derivative is zero
6021r^2-36r=0
r={0,4/669}
so
(2007r3 - 18r2 +178)
increases when r<0
decreases when 0<r<4/669
increases when r>4/669
r=0 (2007r3 - 18r2 +178)->178
r=4/669 (2007r3 - 18r2 +178)->~177.998
So we know there is a real root with r>0
and complex conjugate roots
 

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