Theorem 2.1.6. Existence and Uniqueness Theorem.
Consider the linear equation
\begin{equation*}
ax'' + bx' + cx = g(t)
\end{equation*}
with initial conditions \(x(t_{0}) = x_{0}\) and \(x'(t_{0}) = v_{0}\text{.}\) If \(g(t)\) is continuous on some interval \((t_{1}, t_{2})\) containing \(t_{0}\text{,}\) then there exists a unique solution \(x(t)\) that is continuous on \((t_{1}, t_{2})\text{.}\)