Variation of Parameter Problem

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SUMMARY

The discussion focuses on solving the non-homogeneous differential equation y'' - 6y' + 9y = (x^-3)(e^(3x)) using the method of variation of parameters, specifically addressing the challenge posed by repeated roots. The characteristic equation yields a double root at λ = 3, leading to two independent solutions: e^(-3x) and xe^(-3x). The solution to the entire equation is proposed in the form y(x) = u(x)e^(-3x) + v(x)xe^(-3x), where u(x) and v(x) are functions to be determined through the variation of parameters method.

PREREQUISITES
  • Understanding of second-order linear differential equations
  • Familiarity with the method of variation of parameters
  • Knowledge of characteristic equations and their roots
  • Ability to manipulate exponential functions in differential equations
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  • Study the method of variation of parameters in detail
  • Practice solving second-order linear differential equations with repeated roots
  • Explore the concept of reduction of order for solving differential equations
  • Review examples of non-homogeneous differential equations and their solutions
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Students and professionals in mathematics, particularly those studying differential equations, as well as educators looking for effective methods to teach the variation of parameters technique in the context of repeated roots.

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Homework Statement




Find the general solution using the method of variation of parameters of:

y''-6y'+9y=(x^-3)(e^3x)

I found the roots of the corresponding homogeneous equation to be lamba = 3. So there are repeated roots. My question is, how do I solve a variation of parameter question with repeated roots? I know how to do it using reduction of order but confused on variation of parameters
 
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The same way you solve it without repeated roots! Since x= -3 is a double root of the characteristic equation, two independent solutions to the associated homogeneous equation are [itex]e^{-3x}[/itex] and [itex]xe^{-3x}[/itex].

Look for a solution to the entire equation of the form [itex]y(x)= u(x)e^{-3x}+ v(x)xe^{-3x}[/itex]. Now just follow the usual procedure for variation of parameters.
 

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