Homework Help: Have complimentary, can't get the particular

1. Mar 1, 2012

mistereko

1. The problem statement, all variables and given/known data

d4y/dx4 - a4y = eax

I have found the complimentary to be

Y(x)c = C1eax + C2e-ax + C3Cos(ax) + C4Sin(ax)

I can't seem to get get the particular. I've tried letting Y(x) = Aeax
2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Mar 1, 2012

mistereko

That gives me Aa^4exp(ax) - Aa^4exp(ax) = exp(ax) :(

3. Mar 1, 2012

ehild

Try Y=Ctexp(ax).

ehild

edit: "t" is a typo: It should be Y= Cxexp(ax)

Last edited: Mar 2, 2012
4. Mar 1, 2012

HallsofIvy

ehild means $xe^{ax}$, not $te^{ax}$.

5. Mar 2, 2012

ehild

Thank you, I edited it.

ehild