Diff Eq- Nonhomogeneous Equations

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SUMMARY

The discussion focuses on solving nonhomogeneous differential equations, specifically the equation y^''' + 4y^' = 3x - 1. The solution involves finding a particular solution using the method of Undetermined Coefficients. The correct particular solution is identified as y(x) = (3/8)x^2 - (1/4)x, derived by adjusting the assumed form to y_p = Ax^2 + Bx due to the presence of a constant solution in the homogeneous part. Additionally, the discussion introduces another equation, 4y^'' + 4y^' + y = 3xe^x, emphasizing the need to find the complementary solution first.

PREREQUISITES
  • Understanding of nonhomogeneous differential equations
  • Familiarity with the method of Undetermined Coefficients
  • Knowledge of complementary solutions in differential equations
  • Basic calculus, particularly derivatives and polynomial functions
NEXT STEPS
  • Study the method of Undetermined Coefficients in detail
  • Practice solving various nonhomogeneous differential equations
  • Learn about complementary solutions and their significance
  • Explore advanced topics in differential equations, such as Laplace transforms
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Students and educators in mathematics, particularly those studying differential equations, as well as professionals seeking to apply these concepts in engineering or physics.

Totalderiv
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Homework Statement


Find a particular solution of the given equation.
[tex]y^''' + 4y^' = 3x-1[/tex]

Homework Equations



[tex]r^3 + 4r = 0[/tex]
[tex]r = 0, r = 2i, r = -2i[/tex]

The Attempt at a Solution


[tex]y(x) = Ax-B[/tex]
[tex]y^'(x) = A[/tex]
[tex]y^''(x) = 0[/tex]
[tex]y^'''(x) = 0[/tex]


The answer is:
[tex]y(x)=(3/8)x^2 - (1/4)x[/tex]
But I'm not sure how they came to this, please help!
 
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r=0 gives a constant as a solution of the homogeneous equation. So instead of trying Ax+B you must multiply by x and try ##y_p=Ax^2+Bx##.
 
Totalderiv said:
Thanks! I have another question though,

[tex]4y^'' + 4y^' + y = 3xe^x[/tex]

How do I start this?

The same way you started the other one. You find the complementary solution and then use Undetermined Coefficients for the particular solution. Surely your text discusses the method of Undetermined Coefficients, doesn't it?
 

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