1. The problem statement, all variables and given/known data Calculate velocity. x=position. t=time 2. Relevant equations x=16-12t+2(t^2) 3. The attempt at a solution Derivative of x: v=4t-12 Ok let's try: Equation of x: x=16-12t+2(t^2) Equation of v: v=4t-12 With the equation of x: x(3)=-2 then v(3)=-2/3. Ok, but with the equation of v: v(3)=0. There are different results! Why? What am I doing wrong?