This document provides an overview of higher order homogeneous partial differential equations and their applications. It discusses that a partial differential equation involves a dependent variable and two or more independent variables. Homogeneous equations have solutions called complementary functions where the non-homogeneous term is equal to zero. The auxiliary equation is obtained by replacing the differential operator with the independent variable to find the complementary functions. Several examples are provided to demonstrate finding the complementary functions based on whether the roots of the auxiliary equation are real and distinct or repeated. Applications of partial differential equations discussed include shape processing, feature extraction, and economics.