Diff eq, power series solns, how do i determine how many terms to pull?

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SUMMARY

The discussion focuses on finding two power series solutions for the differential equation y'' - xy = 0 around the ordinary point x = 0. The user sets up the series using the formula y = (c_0)(y_1)[x] + (c_1)(y_2)[x] and expresses the series as a summation. The main challenge is determining how many terms to extract from each series for proper convergence and solution accuracy. It is established that the number of terms pulled from each series does not affect the solution as long as the index k remains consistent across both series.

PREREQUISITES
  • Understanding of differential equations, specifically second-order linear equations.
  • Familiarity with power series and their convergence properties.
  • Knowledge of summation notation and manipulation of series.
  • Basic skills in calculus, particularly Taylor series expansions.
NEXT STEPS
  • Study the method of Frobenius for solving differential equations with power series.
  • Learn about the convergence criteria for power series solutions.
  • Explore the application of power series in solving other types of differential equations.
  • Investigate the relationship between power series solutions and special functions, such as Bessel functions.
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Students and educators in mathematics, particularly those focusing on differential equations, as well as researchers and practitioners seeking to apply power series methods in their work.

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Homework Statement



find 2 power series solutions of the given diff eq about the ordinary point x = 0
y'' - xy = 0

Homework Equations



y = (c_0)(y_1)[x] + (c_1)(y_2)[x]

The Attempt at a Solution



i can set it up to this (sorry idk out how to insert the subscripts with the summation symbols)

{sum n=2} [n (n-1) (c_n) (x ^(n-2) ) ] - {sum n=0} [(c_n) (x ^(n+1) ) ] = 0

but I am not sure how to determine how many terms i need to pull from each series

also, does it matter how many terms i pull so long as my value for k is the same for each series?
 
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You can click on the equation below to see how to write the equation:

\sum_{n=2}^\infty n(n-1)c_n x^{n-2} - \sum_{n=0}^\infty c_n x^{n+1} = 0

The first series starts with a constant term, but the second series begins with the x1 term, so pull the constant term out of the first series and then combine the rest with the terms of the second series.
 

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