Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. An integro-differential equation is an equation which has both integrals and derivatives of an unknown function, such as the equations of basic electric circuit analysis. An integro-differential equation is similar to a differential equation; therefore, tools such as the Laplace transform can possibly be used to solve the equation. If that is the case, the equation or equations are first Laplace transformed and then solved by straightforward algebraic means. The inverse transform of the solution is identified by partial fraction expansion.