An open box with a square base is to be built for $48. The sides of the box will cost $3 per square meter, and the base will cost $4 per square meter. Express the volume of the box as a function of the length of its base.
Suppose the length of its base is a and the height is h.
The the area of the base is a^2, which cost ...
This shows how to express the volume of a box as a function of the length of the base.