For each of the systems shown in Figure, the input is the force f and the outputs

Question:

For each of the systems shown in Figure, the input is the force f and the outputs are the displacements x1 and x2 of the masses. The equilibrium positions with f = 0 correspond to x1 = x2 = 0. Neglect any friction between the masses and the surface. Derive the equations of motion of the systems.