Solve the following initial value problemy′′ + 9y = 3 cos(3x), y(0) = 0, y′(0) = 0 and write the final solution using real valued functions. Sketch the graph of the solution in a x-y diagram.
Can someone help me solve this?
This is what i done so far
y′′ + 9y - 3 cos(3x)= 0
z^2 +9z -3 cos(3x)= 0
z(z+6) + 3(z-cos(3x))=0
Now im really stuck on what to do. Please help. Thanks.