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Firstly Im from japanese and belong to university.I came all the way here cuz my country dont have a proper site to ask. My question is easy so plz help me... The problem is about lecture -That link https://www.youtube.com/watch?v=_xJN3d-d6MI&feature=share

And that specific time is [7:50]

I dont understand why a1=0

Once again,Im sorry i dont know about rules in here so i hope u would be so kind to understand.

The time in Tokyo is 2:09 am, I have to go sleep to go out part job time. So i can come here since 6 hours

Thank you for just reading it!

Alexander
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    Welcome to stackexchange. This is the right site for math questions, but we can't look through a video to find your question. If you write it here in proper mathematical notation and tell us how you started and where you are stuck we may be able to help. Use mathjax: https://math.meta.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference – Ethan Bolker May 06 '20 at 17:16
  • Please make your question self-contained. External links can go stale. – amd May 06 '20 at 18:46

1 Answers1

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You'll notice that we're asked to find two (power series) solutions to this differential equation but without being given an initial value. So there will be infinitely many solutions.
In a power series, the $a_0$ term is the value of the function at the point $y(0)$ about which the series is defined. Since we have not been given a value we can just pick one. The equations is of second order so we also need a value of $y'(0)$ and this coincides with $a_1$ in the power series. Again, since we are not given any information we just pick a value for $a_1$.

Please see the preferred format for asking questions on this website. Good luck!

Nick Castillo
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