ABSTRACT
Following our work with first-order equations, it is natural for us to consider higher-order equations. The first methods of solving differential equations of second or higher-order with constant coefficients were due to Euler. D’Alembert dealt with the case when the auxiliary equation had equal roots. Some of the symbolic methods of finding the particular solution were not given until about 100 years later by Lobatto (1837) and Boole (1859).
