Physics is hard but not that hard

In two ways, a body or object or anything else goes from point 1 to point 2. The first method is to disappear at point 1 and appear at point 2, which is specific to Hollywood, Harry Potter and such things and has nothing to do with physics. But for the second method, which is physical, we need speed. Have you ever travelled the exact distance between two cities with two different cars, one new and fresh and the other old and old? You can see that the arrival time is additional. What is the relationship between distance, time and speed for these three parameters? It is clear that in a specific time with a higher rate, a more fantastic place can be covered, and with a higher speed, a particular location can be covered in a shorter time. That is, the rate has a direct relationship with the site and an opposite relationship with time. So this relationship can be defined for them:

V=Δx/Δt

this speed is for some time and to have the rate at the moment. The moment means exactly the second t and not from t1 to t2. It is enough to make the time interval smaller and smaller, which mathematically means: 

lim(Δt→0) = Δt

Andan this means that the instantaneous speed is equal to:

v=lim(Δt→0)⁡〖Δx/Δt〗=dx/dt