Question

The position function of a particle is given by r(t)= <-3t^2, 5t, t^2+5t>. At what time is the speed minimum?

Answer 1

at t=0

Answer 2

Obviously, but there would be another minimum wouldn't there? If we break it down and integrate to acceleration, we get no t's. All of the t's disappear, right? Or am I missing something?