The position s(t) of an object moving along a straight line is given. Find object's velocity and acceleration and all times where acceleration is 0.

s(t) = 3t^5 - 5t^3 - 7

velocity = s'(t) = 15t^4 - 15t^2

acceleration = s''(t) = 60t^3 - 30t

0=60t^3 - 30t

0=30t(2t^2 -1)

0=t and

0=2t^2 - 1

1=2t^2

1/2 = t^2

square root of 1/2 = t

Hmmmm....I doubt the last part.