A remark on the decay of solutions to the 3-D Navier-Stokes equations

In this paper we derive a decay rate of the L2-norm of the solution to the 3-D Navier-Stokes equations. Although the result which is proved by Fourier splitting method is well known, our method is new, concise and direct. Moreover, it turns out that the new method established here has a wide application on other equations.