Solving 3xy" - 4y' - xy = 0 with Frobenius

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In summary, the Frobenius method is a technique for solving second order linear differential equations with variable coefficients. It involves assuming a solution in the form of a Frobenius series and using the coefficients to determine the values of constants and a constant, known as the indicial point. The method has limitations, such as only being applicable to certain types of equations and potentially failing for equations with repeated or complex roots. The convergence of the Frobenius series solution can be determined using the ratio test.
  • #1
glitchy
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I'm really getting stuck at this and I'm trying to read on it but it's confusing.

I need just a start-up for this equation which is to be solved with the method of frobenius.

3xy" - 4y' - xy = 0

Just need a start.

Any help is appreciated.

Thank you
 
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  • #2
Start by substituting a power series in x for y. y=sum(a_k*x^k). Do the derivatives and equate coefficients of equal powers. Go!
 
  • #3
done, then
 

Related to Solving 3xy" - 4y' - xy = 0 with Frobenius

1. What is the general approach to solving equations with Frobenius method?

The general approach to solving equations with Frobenius method is to assume a solution of the form y(x) = Σn=0 anxn+r, where an are constants and r is a constant to be determined. This is known as the Frobenius series. Substituting this into the given equation and equating coefficients of like powers of x, we can determine the values of an and r to obtain the general solution.

2. What is the significance of the constant r in the Frobenius series?

The constant r in the Frobenius series is known as the indicial or regular singular point. It determines the type of solution we obtain for the given equation. If r is a non-negative integer, the series solution will terminate and we have a polynomial solution. If r is a negative integer, the series solution will have an infinite number of terms and we have a logarithmic solution. If r is a non-integer, the series solution will have an infinite number of terms and we have a power series solution.

3. Can the Frobenius method be used to solve any type of differential equation?

No, the Frobenius method is only applicable to second order linear differential equations with variable coefficients. It cannot be used to solve higher order differential equations or equations with non-linear terms.

4. How do we determine the convergence of the Frobenius series solution?

The convergence of the Frobenius series solution can be determined by applying the ratio test. If the limit of the ratio of consecutive coefficients is less than 1, the series will converge. If the limit is greater than 1, the series will diverge. If the limit is equal to 1, the ratio test is inconclusive and we may need to use other convergence tests.

5. Are there any limitations to using the Frobenius method?

Yes, there are a few limitations to using the Frobenius method. Firstly, it can only be used for equations with variable coefficients, and not for equations with constant coefficients. Secondly, the method may fail for equations with repeated roots, in which case we may need to use other methods such as the reduction of order method. Lastly, the method may not yield a general solution if the equation has complex roots, in which case we may need to use other techniques such as the method of undetermined coefficients.

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