calculus
posted by Sandy .
A particle moves along a horizontal line such that its position s(t) = (t^2e^3t/3)for time t. Find when the particle is at rest.

To be at rest, wouldn't the velocity have to be zero ?
And isn't velocity the first derivative of your s(t) ?
so...
take the first derivative, set it equal to zero and solve for t.
hint: use the product rule.