# Creating bounds on graph that zoom in based on student's input

If I want students to input an equation to see if it graphs as a linear or quadratic function, how can I set the bounds so that if they get creative and go beyond a -10 to 10 boundary that the graph will zoom in for them?

`bounds: makeBounds(a,b,c,d)`

You can make variables that use whatever parameters you want to use for the bounds.

What kind of parameters would you recommend here? Like, if a student is inputting a quadratic equation [for example y = (x - 50)(x+22) or y = -0.01x^2 - 16x + 22], how would we get the bounds to zoom out so that the graph’s “key points” always show up? (i.e. the vertex, y-intercept, and x-intercepts, if applicable)?

Sounds complicated. I mean y-intercept is simple enough. Maybe just use a full-screen graph (only have a graph component), so they can zoom in and out freely.

I’m trying to do something similar to this question so that I don’t have to change the graph every time I make a new activity when graphing different relationships. How do you define a,b,c,d to be the maximum and minimum values when those values can different each time?

You can have some sort of calculation done in the graph and then define variables in the CL pulling those values. In a quadratic, for example, you can calculate A, B, and C (of standard form) in the graph:

``````C=f(0)
B=f'(0)
A=f''(0)/2
``````

Then use the quadratic formula for x-intercepts if present. You could also calculate h and k for the vertex. Add or subtract some units to make max and min values for x- and y-axes. Whatever you name those you can call them into the CL to use for bounds:

``````xmax=this.number(`x_{max}`)
xmin=this.number(`x_{min}`)
...etc
bounds: makeBounds(xmin, xmax, ymin, ymax)
``````

You may have to get creative with calculations depending on your expectations of what student input may be.