when the equation of position is negative its derivative is positive which is velocity which confuses me

Question

there is something that doesn't make sense to me i know that Velocity is the derivative of position fine

now when i differentiate D = T^3 i get the equation of velocity is 3T^2 which is completely okay until T is negative if t is -3

then position is -27 and velocity is 18 which is logically wrong

Answer 1

Suppose you are moving to the right but you are still on the left side of a reference point which we call it $0$

As long as you are on the left side of zero the position is negative and as long as you are moving to the right your velocity is positive.

You may as well get to the right side of the reference point and start moving to the left, which means your position is positive and your velocity is negative.

There is not confusion about it.