The problem statement: A particle travels along the x-axis with uniformly accelerated motion. At times t and s its position is x and y, respectively. Show that its acceleration is a = 2(yt-xs)/ts(s-t). The attempt at a solution: I could be wrong, but it seems to me this problem is ill-posed. Couldn't one solution be a = 0? Couldn't another be that acceleration which gets the particle from rest at (x,t) to (y,s)?