Think about how you might sketch a parabola on a graph. 

1. Do the sides of a parabola ever curve back in like the figure at right? Explain your reasoning.

   Answer (a):

   No, because there is only one $y$-value for every $x$-value in a parabola.

2. Do the sides of the parabola approach straight vertical lines as shown in the figure at right? (In other words, do parabolas have asymptotes?) Give a reason for your answer.

   Answer (b):

   The domain of a parabola is all real numbers, so the graph must extend all the way left and right. Hence it never goes straight up.