21. Derive a model in terms of initial velocity, Vo and displacement, X, for the velocit V. and time taken, t, for a particle which moves along the x-axis so that acceleration is always proportional to its distance from the origin and direct towards it. Assume that when t = 0, x = 0 and V = Vo. Suggest a suitable numerical method to solve the equations (models) so derived (a) above.​