Undergrad Solution of an ODE in series Frobenius method

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The discussion focuses on solving the ordinary differential equation (ODE) given by xy'' + y' + xy = 0 using the Frobenius method. The user is struggling to reverse a series representation of a function J(x) and seeks assistance with this process. The series provided for J(x) and its reciprocal highlight the complexity of the task. Participants question the necessity of reversing the series, suggesting that understanding the context may clarify the need for this step. The conversation emphasizes the challenges of applying series solutions in differential equations.
Caglar Yildiz
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Hi
I am supposed to find solution of $$xy''+y'+xy=0$$
but i am left with reversing this equation.
i am studying solution of a differential equation by series now and I cannot reverse a series in the form of:
$$ J(x)=1-\frac{1}{x^2} +\frac{3x^4}{32} - \frac{5x^6}{576} ...$$

$$ \frac{1}{J}=1+\frac{x^2}{2} +\frac{5x^4}{32}+ \frac{23x^6}{576}...$$

General formula of $J(x)$ is $$\sum_{n=0}^{\infty} \frac{(-1)n}{(n!)^2}(\frac{x}{2})^2$$

Thanks for all help!
 
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Why do you need to reverse it?
 

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