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MathSofiya
Group Title
Use power series to solve the differential equation
\[(x1)y''+y'=0\]
\[y=\sum_{n=0}^\infty a_nx^n\]
\[y'=\sum_{n=1}^\infty na_nx^{n1}\]
\[y''=\sum_{n=2}^\infty n(n1)a_nx^{n2}\]
\[(x1)\sum_{n=2}^\infty n(n1)a_nx^{n2}+\sum_{n=1}^\infty na_nx^{n1}=0\]
 2 years ago
 2 years ago
MathSofiya Group Title
Use power series to solve the differential equation \[(x1)y''+y'=0\] \[y=\sum_{n=0}^\infty a_nx^n\] \[y'=\sum_{n=1}^\infty na_nx^{n1}\] \[y''=\sum_{n=2}^\infty n(n1)a_nx^{n2}\] \[(x1)\sum_{n=2}^\infty n(n1)a_nx^{n2}+\sum_{n=1}^\infty na_nx^{n1}=0\]
 2 years ago
 2 years ago

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MathSofiya Group TitleBest ResponseYou've already chosen the best response.0
allow me to complete this problem as far as I can, give me like 5 mins. Thanks!
 2 years ago

MathSofiya Group TitleBest ResponseYou've already chosen the best response.0
\[\sum_{n=2}^{\infty}n(n1)a_nx^{n1}\sum_{n=2}^\infty n(n1)a_nx^{n2}+\sum_{n=1}^\infty na_nx^{n1}=0\]
 2 years ago

MathSofiya Group TitleBest ResponseYou've already chosen the best response.0
\[\sum_{n=1}^{\infty}n(n+1)a_{n+1}x^n\sum_{n=0}^{\infty}(n+2)(n+1)a_{n+2}x^n+\sum_{n=0}^\infty (n+1)a_{n+1}x^n=0\]
 2 years ago

MathSofiya Group TitleBest ResponseYou've already chosen the best response.0
ok so when we strip out a term on \[\sum_{n=1}^{\infty}n(n+1)a_{n+1}x^n\] for the sum to start at n=0 would I have... \[a_0+ \sum_{n=0}^\infty n(n+1)a_{n+1}x^n \]
 2 years ago

MathSofiya Group TitleBest ResponseYou've already chosen the best response.0
no that would be \[a_0+ \sum_{n=1}^\infty n(n+1)a_{n+1}x^n\]
 2 years ago

mahmit2012 Group TitleBest ResponseYou've already chosen the best response.0
cof of x^n (left)=cof of x^n (right) don't use sigmas.
 2 years ago

mahmit2012 Group TitleBest ResponseYou've already chosen the best response.0
already I have showed you ! Take a look to my solution.
 2 years ago

mahmit2012 Group TitleBest ResponseYou've already chosen the best response.0
y=an y'=(n+1)an+1 xy'=nan y''=(n+2)(n+1)an+2 xy''=(n+1)nan+1 x2y=n(n1)an and so on.
 2 years ago

mahmit2012 Group TitleBest ResponseYou've already chosen the best response.0
(n+1)nan+1(n+2)(n+1)an+2+(n+1)an+1=0 an+2=(n+1)/(n+2) an+1 an+2=a1/(n+2) one answer is just a0(check it out) y=a0+a1sigma(n=1 to inf)(x^n/n)
 2 years ago
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