Hi, everyone! This is my first post here, I need an hand with this equation!
Homework Statement
Solve the initial value problem:
\begin{equation}
\begin{cases}
u''(x)+4u(x)=\cos(2x)
\\u(0)=u'(0)=1
\end{cases}
\end{equation}
The Attempt at a Solution
I started by solving the...