I've been relearning some stuff using khanacademy.org and I am completely lost on the kinematics exercises. I have 5 variables, initial velocity final velocity acceleration time and distance. I am given 3 of them and have to solve for a 4th, which is fine until I have to deal with square roots that gives me 2 solutions. I understand that I may have a negative time solution that isn't possible but some of the exercises produce 2 positive time solutions. Also I can have 2 velocity solutions and I can't figure out which one is right. If I plug my answers back in both answers seem fine. Here is my latest problem... As far as I can tell there is no solution because division by 0 is undefined. So what am I doing wrong?