Undetermined coefficients

In summary, undetermined coefficients are a method used in mathematics to find particular solutions to non-homogeneous linear differential equations. It involves assuming a form for the particular solution and then solving for the undetermined coefficients in that form. This method works by assuming a form for the particular solution of the equation and solving for the undetermined coefficients by equating coefficients of like terms. It is applicable for equations with constant coefficients and simple forcing functions, but has limitations in its applicability and cannot be used for non-linear equations. The advantages of using this method include its simplicity and ability to incorporate initial or boundary conditions, but it may not always give a valid solution for more complex forcing functions.
  • #1
s7b
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How do I go about solving a DE using the method of undetermined coeficients in a question like for example;

y''-4y'+4y=2e^2x

I tried assuming the yp to be Ae^2x but when I plugged it into the DE I ended up with 0=2e^2x


??
 
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  • #2
Since '2' double root of your aux. eq'n.

the yp should be Ax^2e^2x
 
  • #3
Once you substitute back into the original DE
Do you get:

8Ax^2e^2x + 2Ae^2x = 2e^2x
 

1. What are undetermined coefficients?

Undetermined coefficients are a method used in mathematics to find particular solutions to non-homogeneous linear differential equations. It involves assuming a form for the particular solution and then solving for the undetermined coefficients in that form.

2. How does the method of undetermined coefficients work?

The method of undetermined coefficients works by assuming a form for the particular solution of a non-homogeneous linear differential equation, typically based on the form of the forcing function. The undetermined coefficients in the assumed form are then solved for by substituting the form into the original equation and equating coefficients of like terms.

3. When is the method of undetermined coefficients applicable?

The method of undetermined coefficients is applicable when the non-homogeneous linear differential equation has constant coefficients and the forcing function is a polynomial, exponential, sine or cosine function. It is not applicable for more complex forcing functions such as logarithmic or hyperbolic functions.

4. What are the advantages of using undetermined coefficients?

The method of undetermined coefficients is advantageous because it is a relatively simple and straightforward method for finding particular solutions to non-homogeneous linear differential equations. It also allows for the easy incorporation of initial or boundary conditions into the solution.

5. Are there any limitations to the method of undetermined coefficients?

Yes, the method of undetermined coefficients has limitations in its applicability, as mentioned in question 3. It also cannot be used for non-linear differential equations, and the assumed form for the particular solution must not be a solution to the homogeneous equation. Additionally, it may not always give a valid solution for more complex forcing functions.

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