I was thinking of doin that, but then i thought to realy "prove" it that way, you would have to test a whole lot of points. Its one of those questions that common sense can tell you the answer straight away, but we gotta show it. But really, i dont think they would take marks of you. Well donec_james said:Yeah, I understand what you mean, but you could've done the question without even having to find the second derivative by using the first derivative test - that is, you could've just tested points on either side. Much less messy and time consuming for that particular question.