I am new to Mathematica. How do I make a graph range 20 x 20? like
(-20,20) (-20,-20) (20,20) (20,-20)
I do not understand the question. May be you can post an image. But just in case, you can look at GridLines as in
Plot[{}, {x, -20, 20}, PlotRange -> {{-20, 20}, {-20, 20}},
GridLines -> {Range[-20, 20, 2], Range[-20, 20, 2]}, GridLinesStyle -> LightRed, Frame -> True]
