Prove that if $L[\mathbf{u}]=\mathbf{f}$ is a real inhomogeneous linear system with real right-hand side $\mathbf{f}$, and $\mathbf{u}=\mathbf{v}+\mathrm{i} \mathbf{w}$ is a complex solution, then its real part $\mathbf{v}$ is a solution to the system, $L[\mathbf{v}]=\mathbf{f}$, while its imaginary part $\mathbf{w}$ solves the homogeneous system $L[