This document discusses the method of undetermined coefficients for solving nonhomogeneous second-order linear differential equations. It explains that the solution to a nonhomogeneous equation is the sum of the solution to the corresponding homogeneous equation and a particular solution to account for the nonhomogeneous term. It also outlines the steps to use the method of undetermined coefficients, which involves guessing a form for the particular solution based on the type of nonhomogeneous term and solving for the coefficients.