Question
An open box with a square base is to be made out of a given quantity of sheet of area c2. Show that the maximum volume of the box is 
Solution
Let x be the side of the square base of the open box and y be its height. Let V denote the volume of the box.
...(1)
Also surface area = c2
For V to be maximum or minimum,
...(1)Also surface area = c2
For V to be maximum or minimum,
