Solving D.E. with Variation of Parameters Technique

In summary, the conversation discusses solving a differential equation using the variation of parameters technique. The equation given is a Bernoulli equation, which needs to be transformed into a linear equation with constant coefficients. The speaker suggests using the substitution x=e^t to solve the equation.
  • #1
RadiationX
256
0
I need to solve this D.E.

[tex]x^2y''-xy' + y = x^3[/tex]

i'm supposed to use the variation of parameters technique.

in that technique i need to get a coeffecient of 1 in the first postion of y'' and then sove the homogenous D.E.

[tex]y''-\frac{y'}{x} +\frac{y}{x^2}=0[/tex]

the above leads to

[tex] m^2-2m +1=0[/tex]

now solving this i get

[tex]C_1x +C_2tx[/tex]

my problem is that i don't know how to move forward with
[tex]C_2tx[/tex]

how do i proceed
 
Last edited:
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  • #2
It's an Euler equation.You need to transform it into a linear equation with constant coeffs.Read the theory again and identify the substitution you need.

Daniel.
 
  • #3
do you mean that this is a Bernoulli equation?
 
  • #4
I told u it was/is an Euler eqn.

Make the sub

[tex] x=e^{t} [/tex]

[tex] y(x)\longrightarrow \bar{y}(t) [/tex]

Daniel.
 
Last edited:
  • #5
ok. i'll figure it out
 

1. What is the variation of parameters technique?

The variation of parameters technique is a method used to solve differential equations that cannot be solved using other techniques, such as separation of variables or integration factors. It involves finding a particular solution by varying the constants in the general solution of the homogeneous equation.

2. When should I use the variation of parameters technique?

You should use the variation of parameters technique when the differential equation is in the form of y'' + p(x)y' + q(x)y = f(x), where p(x) and q(x) are continuous functions and f(x) is a nonhomogeneous function. This method is not applicable for equations with constant coefficients or non-linear equations.

3. How do I use the variation of parameters technique to solve a differential equation?

To use the variation of parameters technique, follow these steps:
1. Find the general solution of the homogeneous equation by setting f(x) = 0.
2. Find the particular solution by assuming a general form of y_p(x) = u(x)y_1(x) + v(x)y_2(x), where y_1(x) and y_2(x) are the linearly independent solutions of the homogeneous equation.
3. Solve for u(x) and v(x) by substituting the particular solution and its derivatives into the nonhomogeneous equation.
4. The general solution of the nonhomogeneous equation is then given by y(x) = y_h(x) + y_p(x), where y_h(x) is the general solution of the homogeneous equation and y_p(x) is the particular solution found in step 2.

4. What are the advantages of using the variation of parameters technique?

The variation of parameters technique allows you to solve nonhomogeneous differential equations without the need for guessing a particular solution. It also provides a general solution that includes both the homogeneous and particular solutions, giving a complete solution to the equation. Additionally, this method can be applied to a wide range of nonhomogeneous equations.

5. Are there any limitations to the variation of parameters technique?

Yes, there are some limitations to the variation of parameters technique. This method can only be applied to linear differential equations with continuous coefficients and nonhomogeneous terms. It also requires finding the linearly independent solutions of the homogeneous equation, which can be challenging for more complex equations. Additionally, the variation of parameters technique may not work for all nonhomogeneous equations and may require the use of other techniques or numerical methods.

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