When taking 2x units from each side, the dimensions of our box are the
following:
The volume of a box V is found by the following formula:
Thus,
We want to maximize this equation. We can see when this equation is maximized
by looking at various values for x. We know that in order for our
equation to make any sense, x only exists within the interval (0,
2.5), otherwise volume will be negative. Consider the following table:
According to the table, a value of x = 1 will maximize the volume of
the box. If we take a look at the graph of these values we can easily see
that the maximum volume of the box is 18.