I am having some problems with some homework questions, I was hoping maybe somebody could help me work these out so I had some reference material for the rest of my homework.

Find the absolute maximum, and minimum, if any, on the interval [0,9]

f(x)=1/8x^2 - 4sqrtx

need f prime of (x)

critical values

absolute min, and max

and

Exponential Functions

If an open box has a square base and a volume of 108 inches cubed, and is constructed from a sheet of tin, find the dimensions of the box that will use the minimum amount of material in it's construction.