(15 points) Consider the wave equation with conditions
\begin{equation*}
u_{tt} = \frac{1}{9} u_{xx},
\end{equation*}
$u(0, t) = 0$, $u(4, t) = 0$, $u(x, 0) = egin{cases} x, & 0 < x < 2, \ 4 - x, & 2 \le x < 4 \end{cases}$, $u_t(x, 0) = 0$
Write the terms up to $n = 3$ in the series solution and graph the solution using Mathematica.