Since you title this "notation", I must confess that I have no idea what this is suppose to mean. I assume that you just dropped the "2" in but that should be "= 0" not "= x". Also the left side of the equation is a set, the right side is not. You should have "{-1, 2}" on the right side: . Since you were not asked for the intercepts, what does this "answer"?

There is no "therefore" here. Yes, but that is not true[tex]B)

becausey'= 2x-1. If you want to say those are the critical numbers, saythat.

Again, you don't say what this is supposed to answer. If you mean that (1/2, -2.25) is the only critical point say so.

Well, strictly speaking theC)

D opens up.graphof opens upward, but that's fairly common "abuse of notation".

And, specifically, is the vertex of the parabola.I don't know how to graph on latex but i would put a points at and draw an upward opening parabola.

Am i using them correctly? Any suggestions on better usage?

Thanks.