motion of a particle is x=(6t-3)(t^2+1) where x is in meters and t is in seconds. what is the instantaneous velocity of the particle at time equals 3 seconds

Question

the motion of the particle is given by x=(6t-3)(t^2+1)

Answer 1

The instantaneous velocity is equal to the derivative of x(t) wrt t, dx(t)/dt.  So take dx(t)/dt using the product rule (alternatively, multiply it out), then plug in t = 3 sec.  Units are m/s.