1. The problem statement, all variables and given/known data A particle has displacement x(t) = (t^3 - t^2)e^-t for times 0=<t=<9. Find its velocity v(t) and determine for what times the particle is moving in the positive x direction. 2. Relevant equations Differentiating x(t) you get v(t)=-t(t^2-4t+2)e^-t 3. The attempt at a solution I differentiated the equation but I am lost on how to get the times it is moving in the positive x direction.