8.1 Introduction8.2 Order, linearity and homogeneity of a partial differential equation8.2.1 Order8.2.2 Linearity8.2.3 Homogeneity8.3 Origin of partial differential equation8.4 Formation of partial differential equation by elimination of two arbitrary constantsExercise 8.18.5 Formation of partial differential equations by elimination of arbitrary functionsExercise 8.28.6 Classification of first-order partial differential equations8.6.1 Linear equation8.6.2 Semi-linear equation8.6.3 Quasi-linear equation8.6.4 Non-linear equation8.7 Classification of solutions of first-order partial differential equation8.7.1 Complete integral8.7.2 General integral8.7.3 Particular integral8.7.4 Singular integral8.8 Equations solvable by direct integrationExercise 8.38.9 Quasi-linear equations of first order8.10 Solution of linear, semi-linear and quasi-linear equations8.10.1 All the variables are separable8.10.2 Two variables are separable8.10.3 Method of multipliersExercise 8.48.11 Non-linear equations of first orderExercise 8.58.12 Euler's method of separation of variablesExercise 8.68.13 Classification of second-order partial differential equations 8-548.13.1 Introduction8.13.2 Classification of equations8.13.3 Initial and boundary value problems and their solution8.13.4 Solution of one-dimensional heat equation (or diffusion equation)Exercise 8.78.13.5 One-dimensional wave equation8.13.6 Vibrating string with zero initial velocity8.13.7 Vibrating string with given initial velocity and zero initial displacement8.13.8 Vibrating string with initial displacement and initial velocityExercise 8.88.13.9 Laplace's equation or potential equation or two-dimensional steady-state heat flow equationExercise 8.9