Show that in the \(3 \times 3\) system \(\mathbf{X}^{\prime}=\mathbf{A X}\) with
the eigenvalue \(\lambda\) of multiplicity 3 with one corresponding (linearly
independent) eigenvector \(\mathbf{v}_{1}\), three linearly independent
solutions of the system are \(\mathbf{X}_{1}=\mathbf{v}_{1} e^{\lambda t},
\mathbf{X}_{2}=\) \(\left(\mathbf{v}_{1} t+\mathbf{w}_{2}\right) e^{\lambda t}\),
and \(\mathbf{X}_{3}=\left(\frac{1}{2} \mathbf{v}_{1} t^{2}+\mathbf{w}_{2}
t+\right.\) \(\left.\mathbf{u}_{3}\right) e^{\lambda t}\), where \(\mathbf{u}_{3}\)
satisfies \((\mathbf{A}-\lambda \mathbf{I}) \mathbf{u}_{3}=\mathbf{w}_{2}\) and
\(\mathbf{w}_{2}\) satisfies \((\mathbf{A}-\lambda \mathbf{I})
\mathbf{w}_{2}=\mathbf{v}_{1}\).