Question

use the points to describe a corresponding system of functions (9,9)(-9,9)(-9,-9)(9,-9)

Answer 1

dwing out your lines on the x y plane you can see that this a box. You have
\[x=9, and x=-9, -9\le y \le 9\]
that is "x is the vertical line at 9 and at -9 while y varies from -9 to 9" and you can switch those around.