The corresponding homogeneous equation is with the characteristic equation . If and are two real roots of the characteristic equation, then the general solution of the homogeneous differential equation is , where and are arbitrary constants. If , the general solution is . If , the general solution is .

To find a particular solution of the nonhomogeneous equation, the method of variation of parameters (Lagrange's method) is used. The solution has the form , where and are independent partial solutions of the corresponding homogeneous equation, and and are functions of satisfying the system of equations

,

Define the Wronskian by . Then , .

The general solution of the nonhomogeneous equation is the sum of the general solution of the homogeneous equation and a particular solution of the nonhomogeneous equation.