You need to put all these equations in your calculator, and fix "Window" to where all X and Y max's are 1, and all X and Y min's are 1. This lets you see how wide/ narrow they are up closer. And since you are just looking for the widest and most narrow and so on, I would change the -4x^2 to just 4x^2. Positives and negatives don't matter.
If you have to, go to"Trace" and use the up and down arrows on your calculator(use right/ left to go further up in the graph). You can then see all 3 functions up close, and you can determine which ones are each.
Using common sense, you can see the answers, widest to narrowest, in order, are 2x^2, -4x^2(make it negative again), and 5x^2.
To order the group of quadratic functions from widest to narrowest graph, you will need to draw the graphs. First, create a range for the y values, such that y=0, 1, 2, 3 and so on. Then, get the corresponding values of x for each function and then draw the graphs.