Differential equations and series

freshman2013
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1.

1.Homework Statement


Use power series to evaluate intial value problem y''-xy'-2y=4x^2 y(0)=1 and y'(0)=1

Homework Equations

The Attempt at a Solution


I got the series Cnx^n and took its derivative and plugged it into the formula and I got but when I factor out x^n and set that experssion equal to 4x^2, I realize I'm stuck and I'm not sure If I'm doing it correctly.
 
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freshman2013 said:
1.

1.Homework Statement


Use power series to evaluate intial value problem y''-xy'-2y=4x^2 y(0)=1 and y'(0)=1

Homework Equations




The Attempt at a Solution





I got the series Cnx^n and took its derivative and plugged it into the formula and I got but when I factor out x^n and set that experssion equal to 4x^2, I realize I'm stuck and I'm not sure If I'm doing it correctly.

What that tells you is that coefficient of x^2 on the left hand side is 4, and the coefficient of every other power of x on the left hand side is zero.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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