Question: Substrat using Maple

Dear All;

Happy, to discuss with you these lines, and thank you to help me.

My goal is:

ode := D(y)(x) = f(x,y(x));
                          
In this expression, is assumed to be a known function of the independant variable
                                      x
 and the function that we are trying to solve for
                                    y(x)
.  The simplest numerical stencils to solve this equation will give us an approximation to
                                      y
 at some point
                                  x = X + h
 given some knowledge of
                                      y
 at
                                    x = X
.  All of these stencils are based on the Taylor series approximation for
                                    y(x)
 about
                                    x = X
 to linear order:
eq1 := y(x) = series(y(x),x=X,3);
                       
eq2 := h = x - X;
eq3 := subs(isolate(eq2,x),eq1);
                                
Now, we can remove the first derivative of y
                                     
 by making use of the differential equation:
eq4 := subs(x=X,ode);
eq5 := subs(eq4,eq3);
                           

Now we must compute the same for y(x-h)  and then make.  How can I do this please