It is well known that the famous D'Alembert formula for solving the wave equation of secondorder is a very important instrument in the study of the dynamics of waves. It is also obvious that D'Alembert's solutions for higher-order partial differential equations are of great importance. In this paper, the D'Alembert solutions of the Cauchy problem for linear partial differential equations with homogeneous constant coefficients of the third-order are obtained. Finally, using the obtained solutions, some computer tests on three distinct roots have been carried out. The results clearly indicate the dispersion dynamics of waves with some initial profile.