The exact solution of the boundary value problem

,

at

, and

at

with parameter

is

.
The second-order discretization for the discrete variable

at points

with step size

gives the recurrence equation

, where

,

, which is solved exactly using
Mathematica's
RSolve function.
The difference between the finite difference and exact solutions in the region

is dynamically plotted in the solution region

for 3 to 300 discretization points and parameter

between -10 and 10.
By using
DSolve and
RSolve, a numerical solution is completely avoided.