We can solve this equation for by substituting the expression given at the beginning, that is . To get an expression for the factor, we simply have to differentiate twice and approximate it again in the same way we did this above: If we now substitute this to the preceding equation, we get or This yields the Numerov's method if we ignore the term of order . It follows that the order of convergence (assuming stability) is 4. References . This book includes the following references: . . Numerical differential equations