Good day everyone. I'm confused about how I SHOULD set up the domain of my function that models the word problem. Suppose I have a word problem that goes like this: A square box with no top is to be made by cutting congruent squares from the four corners of a square metal sheet and then folding up the resulting flaps. If the length of a side of the metal sheet is 12 in., how should the square be cut in order to make a box with the largest possible volume? Okay, so my volume equation is V(x)=(12-2x)(12-2x)(x) I know how to solve this kind of equation but, how do I know what interval I should consider? Should I use [0,6] or (0,6)? Can anyone give tips on how to know which one? My book used (0,6) but I don't really understand why. I know its meaningless to say you cut the corners by 0 cm^2, since you didn't really cut anything. Also 6cm^2, since by then none will be left for the open-top box. But how do I really know the domain of my function? I'm really confused. Help would be really appreciated.