Well, I'm having trouble doing optimization problems (maximizing and/or minimizing a function in more then one variable with/without constraints). Would be a great help if someone could give me some good links on this topic or some methods generally. If the domain is compact; where are the points that could possibly maximize/minimize the function? Is it either points that satisfy the equation [itex]\nabla[/itex][itex]f = 0[/itex] and points on the boundary? In one problem I did, the point that maximized the function didn't satisfy [itex]\nabla[/itex][itex]f = 0[/itex], how come? How do I examine the boundary? if the domain is defined by an inequality and the equality corresponds to the boundary, do I just solve for either variable and plug into the original equation? What if it's a three variable function? If the domain isn't compact, and both x and y go from 0 to infinity, what do I do then?