Differential Equation with an Initial condition

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Homework Help Overview

The discussion revolves around solving a differential equation of the form x(dy/dx) = 3y + x^4cos(x) with the initial condition y(2π) = 0. The subject area is differential equations, specifically first-order equations.

Discussion Character

  • Exploratory, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss attempts to separate the variables in the equation, noting difficulties with carrying over terms. There is mention of trying a Bernoulli differential equation method and the need for a change of variable. Some participants suggest using integrating factors and rearranging the equation into a standard form.

Discussion Status

The discussion is ongoing, with participants exploring different methods to approach the problem. Hints have been provided regarding integrating factors and rearranging the equation, but no consensus or final solution has been reached.

Contextual Notes

Participants are working under the constraints of the initial condition and the specific form of the differential equation, which has led to various interpretations and approaches being discussed.

Zinggy
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Homework Statement


x(dy/dx) = 3y +x4cos(x), y(2pi)=0

Homework Equations


N/A

The Attempt at a Solution


I've tried a couple different ways to make this separable, but you always carry over a 1/dx or 1/dy term and I can never fully separate this. I've also tried to do a Bernoulli differential equation method by doing a change of variable and putting it in the form: xy'-3y = x4cos(x) but it's not quite the right format to allow that to work, I would need it to be y4cos(x) instead.
 
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Hint: Integrating factors.
 
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Zinggy said:

Homework Statement


x(dy/dx) = 3y +x4cos(x), y(2pi)=0

Homework Equations


N/A

The Attempt at a Solution


I've tried a couple different ways to make this separable, but you always carry over a 1/dx or 1/dy term and I can never fully separate this. I've also tried to do a Bernoulli differential equation method by doing a change of variable and putting it in the form: xy'-3y = x4cos(x) but it's not quite the right format to allow that to work, I would need it to be y4cos(x) instead.
Divide both sides of the DE by ##x##. That gives a very standard first-order DE with a well-known solution. (Hint: the hint from #2).
 
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Divide both sides by ##x## and rearrange into:
##\dot y -\frac 3 x y = x^3 cos(x)##
Since you are studying differential equations I trust that you can figure out how to solve this.
 

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