1. The problem statement, all variables and given/known data Eliminate t from the equation (x-xi)=vi(t)+1/2(a)t^2 using the kinematic equation v=vi+at to get v^2=vi^2+2a(x-xi) 3. The attempt at a solution I wind up with (x-xi)=vi(v-vi/a) + 1/2(v^2-vi^2/a). If the first term on the right side didn't exist, I could see what the solution is, but I can't see why it just seems to disappear. here is a video showing the exact step where I get lost. Again, the first term on the right just disappears. I can see why that would happen if the initial velocity is 0, but what if it isn't?