The purpose of this program is to implement Galerkin method over "ne" individual elements for solving the following general 2nd order,
homogeneous, Boundary Value problem (BVP) with constant coefficients, and then comparing the answer with the exact solution.

ax"(t)+bx'(t)+cx(t)=0 for t1<=t<=t2
BC: x(t1)=x1 and x(t2)=x2

>> BVP_Galerkin(a,b,c,t1,t2,x1,x2,ne)
where "ne" is the number of elements

The output of this program is
1- The approximated x(t) vs. exact x(t)
2- The approximated x'(t) vs. exact x'(t)
3- The approximated x"(t) vs. exact x"(t)

Example:
x"(t)+ 0.5x'(t)+ 10x(t)=0
BC: x(1)=2, x(10)=0;
Solution: We have: a=1;b=2;c=3;
t1=1;t2=10;
x1=2;x2=0;
Using ne=128 elements,
>>BVP_Galerkin2(1,2,3,1,10,2,0,128)