- #1

andrew.c

- 46

- 0

## Homework Statement

Find the general and, if possible, particular solutions of the following ordinary differential equations:

y''+9y=36sin3x

*(hint: modification rule for PI)*

## Homework Equations

Knowledge of ODE's

[tex]y = y_{aux}+y_{particular}[/tex]

## The Attempt at a Solution

I get the compementary function;

y''+9y = 0

and then using lambda-notation

[tex]\lambda^2 + 9 = 0[/tex]

therefore

[tex]\lambda = \pm 3i[/tex]

(complex roots)

so

[tex]y_{aux} = A cos 3x + B sin 3x[/tex]

but now how do I get [tex]y_{particular}[/tex]??