Finding Particular Solutions for Second Order Linear Differential Equations

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In summary, the Method of Undetermined Coefficients is a mathematical technique used to solve linear non-homogeneous differential equations by guessing the form of the solution and using the coefficients to solve for unknown constants. It is typically used when the non-homogeneous term is a polynomial, exponential, sine, cosine, or a combination of these functions. The method involves finding the general solution to the associated homogeneous equation, guessing a particular solution, and adding it to the general solution to get the final solution. However, the method may not work for all types of non-homogeneous terms and may fail if the guess for the particular solution is not linearly independent from the general solution. In such cases, the method of variation of parameters can be
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strawberrysk8
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Homework Statement



Find particular solution for
y''+2y'+5y = 4(e^-t)cos2t

Homework Equations



y.c = C(e^-t)cos2t + C(e^-t)sin2t

The Attempt at a Solution



y.p (particular solution) = At(e^-t)cos2t + Bt(e^-t)sin2t does not work! Help please!
 
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  • #2
Are you sure your [itex]y_p[/itex] doesn't work? Why don't you show us what you're getting when you plug it into the ODE.
 
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reply oh i figured it out. thank you!
 

FAQ: Finding Particular Solutions for Second Order Linear Differential Equations

What is the Method of Undetermined Coefficients?

The Method of Undetermined Coefficients is a mathematical technique used to solve linear non-homogeneous differential equations. It involves finding a particular solution to the equation by guessing the form of the solution and then using the coefficients in the guess to solve for the unknown constants.

When is the Method of Undetermined Coefficients used?

The Method of Undetermined Coefficients is typically used when the non-homogeneous term in a differential equation is a polynomial, exponential, sine, cosine, or a combination of these functions. It is also used when the equation has constant coefficients.

How does the Method of Undetermined Coefficients work?

The method works by first finding the general solution to the associated homogeneous equation. Then, a particular solution is guessed based on the form of the non-homogeneous term. The coefficients in the guess are then substituted into the original equation to solve for the unknown constants. The general solution and particular solution are then added together to get the final solution.

What are the limitations of the Method of Undetermined Coefficients?

The method may not work for all types of non-homogeneous terms. It may fail if the guess for the particular solution is not linearly independent from the general solution of the associated homogeneous equation. In these cases, the method of variation of parameters may be used instead.

Are there any real-world applications of the Method of Undetermined Coefficients?

Yes, the method is commonly used in physics and engineering to solve differential equations that model real-world systems. For example, it can be used to model the motion of a mass-spring system or the decay of a radioactive substance.

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