The problem is from the MIT Open CourseWare Calculus eBook by Strang. Chapter 12.2, #3: A ball is thrown at 60 degrees with initial velocity of 20m/sec to clear a wall 2m high. How far away is the wall? Finding flight time T, range R, and max height Y(max) is the easy part. How do I find how far away the 2m-high wall is? I understand that this has two solutions (the wall is going to be really close to the launch point, or really close to the end point). How do I calculate the solutions? Please note that it's been a very long time since Physics I. I've attempted to take the Range and subtract the height of the wall from it, but that doesn't work. I feel like instead of Y(max) I need Y(2m), but I don't know how to do that. You don't need to work out the problem - a link to an example or a little push is all I'm looking for here. Thanks!