\begin{exerciseStatement}
Explain how to find the particular solution to each given IVP.
\begin{enumerate}[(a)]
\item \[ -{x''} - 4 \, {x} = 0 \hspace{2em}
{x} (0)= 1 ,
{x} '(0)= 8 \]
\item \[ -{y''} - 12 \, {y} = 7 \, {y'} \hspace{2em}
{y} (0)= -1 ,
{y} '(0)= 2 \]
\end{enumerate}
\end{exerciseStatement}
\begin{exerciseAnswer}
\[ {x} = \cos\left(2 \, t\right) + 4 \, \sin\left(2 \, t\right) \]\[ {y} = -2 \, e^{\left(-3 \, t\right)} + e^{\left(-4 \, t\right)} \]
\end{exerciseAnswer}