If I'm not mistaken you would use the Vertex formula which is (x= -b / 2(a)). Its the first part of the quadratic formula. This would help you find the maximum height of the object. It's been a semester since i've taken my last algebra class that I ever want to take in my life, but I don't want to tell you anything else because it may be wrong. I hope this helps you a little. I worked hours on end a day everyday on Math lab and I know how that working on line goes. I can feel your stress/ pain haha. Hope you figure it out.