I really have no idea where to even begin with this problem. I did some guess and check, but I'm sure there's some method I'm suppose to use that we haven't covered. I understand what it's asking and all, but I'm at a loss as to how to solve it.

Consider the graph of

$\displaystyle

y = \sqrt{x} $

limited to the domain of (0,9).

Find the largest rectangle that can be constructed inside of that shape, with sides parallel to the x- and y-axes and the right edge of the rectangle being the vertical line x = 9.