Undetermined coefficient method

In summary, the undetermined coefficient method is a mathematical technique used to solve non-homogeneous linear differential equations by assuming a form for the solution and determining the coefficients that satisfy the equation. It is typically used for equations with simple non-homogeneous terms and works by assuming a particular solution and solving for the coefficients. However, it has limitations such as only working for linear equations with constant coefficients and being difficult to apply for complex non-homogeneous terms. It can also be used for higher order differential equations, but the complexity of finding the particular solution and coefficients increases with the order of the equation. Other methods, such as variation of parameters, may be more efficient for solving higher order differential equations.
  • #1
masterchiefo
212
2

Homework Statement


y''+10y'+25y=x+2+3e-5*x

Homework Equations

The Attempt at a Solution


F(D) = D2+10D+25 zeroes: -5
yc= C1*e-5*x + C2*e-5*x *x

yp = ax+b + C*e-5*x
yp = ax+b + C*e-5*x*x2

I just want to know if my yc and yp is correct, after that I know how to do it.
 
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  • #2
yc is correct, yp is not. The SECOND yp, [itex]ax+ b+ cx^2e^{-5x}[/itex] is correct. Since [itex]e^{-5x}[/itex] and [itex]xe^{-5x}[/itex] satisfy the associated homogenous equation you need the "[itex]x^2[/itex]".
 

Related to Undetermined coefficient method

1. What is the undetermined coefficient method?

The undetermined coefficient method is a mathematical technique used to solve non-homogeneous linear differential equations. It involves finding a particular solution to the equation by assuming a form for the solution and then determining the coefficients that satisfy the equation.

2. When is the undetermined coefficient method used?

This method is typically used when the non-homogeneous term in a linear differential equation has a simple form, such as a polynomial, exponential, or trigonometric function. It is also useful when the non-homogeneous term has the same form as the complementary solution.

3. How does the undetermined coefficient method work?

The undetermined coefficient method involves two main steps. First, a particular solution is assumed based on the form of the non-homogeneous term. Then, the undetermined coefficients are determined by plugging the assumed solution into the differential equation and solving for the coefficients.

4. What are some limitations of the undetermined coefficient method?

One limitation of this method is that it only works for linear differential equations with constant coefficients. It also may not work if the assumed form of the particular solution is already a solution to the homogeneous equation. Additionally, if the non-homogeneous term is too complex, this method may be difficult to apply.

5. Can the undetermined coefficient method be used for higher order differential equations?

Yes, the undetermined coefficient method can be used for higher order differential equations. However, as the order of the equation increases, the complexity of finding the particular solution and determining the coefficients also increases. In some cases, it may be more efficient to use other methods, such as variation of parameters, to solve higher order differential equations.

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