x1 = x;
t = t + dt; // i can't seems to create the difference in the value of x to be assigned to x2 and x1 differently despite the the line of code t = t+ dt;
x2 = x;
v = (x2 - x1)/dt;

but i seems to get no value for v.

it shouldn't be that difficult, but i can't figure out.

can save me? ;D