This lecture covers the method of finding a particular solution of a second-order linear differential equation with constant coefficients using the method of undetermined coefficients. It also explains the demonstration methods, including demonstration by absurdity. The lecture progresses to the general solution of the complete equation and the principle of superposition of solutions. Additionally, it delves into the method of indefinite coefficients and the variation method for solving differential equations. The lecture concludes with a detailed explanation of the characteristic equation and the application of the method of indeterminate coefficients.