The remarkable proportion in this case differs slightly from the linear examples:
we see that the denominator involves the A concentrations of both trajectories, AA and AB. Only this can ensure a ratio that equals the equilibrium constant at every time t > 0
3.2. Nonlinear reversible reaction (forward and backward second order)
The mass conservation law is
which offers no difficulties for the initial values, (1,0) and (0,1). The differential equation
can be solved analytically as
Again eliminating time, the similar proportion for this case is
where both numerator and denominator have undergone a dupli- cation in A and B trajectories, still producing the equilibrium constant at all times t > 0.