You know the trough optimization problems. I used to be able to do these easily and I completely forgot how to do them so I need help.
Trapezoids are 1/2h(a+b), in this case a is the long side, and we're trying to maximize area, which in this case will be y. We know that y and both sides of the trapezoids are 12", so by this we know that h^2=12^2 - .5(a-b)^2. However, if we plug this in and derive we end up with impenetrable square-root barf. I know that there's an easier way to do this. Help?