y = A cos 2x + B sin 2x...that would be the complementary solution. How would I go about finding a particular integral? I was going to do an integrating factor but I think that's only for first-order ODE.
For the most part. If it were y'' + 4y = 0, I'd know what to do. But for some reason, I'm at a mental block with this. Or is this something completely different from what you're asking?
Trying to solve the following boundary value problems.
y'' + 4y = cos x; y(0) = 0, y(pi) = 0
y'' + 4y = sin x; y(0) = 0, y(pi) = 0
The answer key says that there's no solution to the first part, but there is a solution to the 2nd part. I'm really lost and am not sure how to go...