- #1
fluidistic
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Homework Statement
Hello guys. I'm totally stuck at finding the solution to ##y'''-12y'+16y=32x-8##.
Homework Equations
Variation of parameters once I'm done with the general solution to the homogeneous ODE.
The Attempt at a Solution
First I want to solve the homogeneous ODE ##y'''-12y'+16y=0## and then use variation of parameters to solve ##y'''-12y'+16y=32x-8## or maybe I'll propose a solution such as a polynomial of degree 4, ##P_4(x)=a_0+a_1x+a_2x^2+a_3x^3+a_4x^4## to find the particular solution of the ODE.
So, dealing with the homogeneous ODE, I'm totally stuck. I tried to get the characteristic equation, it is worth ##r^3-12r+16=0## so it's not a piece of cake to get the 3 values of r which satisfy that equation. I could not do it.
I tried to seek a solution in terms of infinite series and since there's no singular point I sought for a solution of the type ##\phi (x)=\sum _{n=0}^\infty a_n x^n##. Which eventually lead me to [tex]\sum _{n=0}^\infty n(n-1)(n-2)a_n x^{n-3}-12\sum _{n=0}^\infty a_n n x^{n-1}+16 \sum _{n=0}^\infty a_n x^n=0[/tex]. I did not proceed further in that direction because from here I notice that I'll get ##a_{n+3}## in terms of ##a_{n+1}## and ##a_n## which turns out to be incredibly messy. I was expecting to get a single coefficient in terms of another single coefficient.
This is where I ran out of ideas. I'm looking for any idea guys to tackle this ODE. Thank you.