# Dynamic Market Equilibrium: motivation for differential equations

I came across this discussion, claiming supply and demand are expressible in terms of its price as $$Q_s=c_1+w_1P+u_1P'+v_1P'',\,Q_d=c_2+w_2P+u_2P'+v_2P''.$$Equating supply to demand for an equilibrium gives an ODE one can solve, but where do these formulae for $Q_s,\,Q_d$ come from?

I apologise if, contrary to the impression the page gives, these equations are not a mainstream model.