So here's where I am now. I need to find the minimum of the following function:

I have absolutely no idea where to begin.

On this one, I need the maximum:

Again, don't know what to do here.

Then there's this other problem that wants me to find the "price that will yield the maximum revenue" and the maximum revenue itself:

It firsts asks me to find the revenue earned for each price given, which were $4, $6, and $8. So the earned revenue would be:

R ($4) = $432

R ($6) = $504

R ($8) = $480

Back to finding the price that will give the maximum revenue, I chose $6, because, according to those prices and revenue earned, $6 brought in the most, at $504, but these two were wrong. So I don't know what to do.