Coding challenge: plotter in p5.js

I'd like to see a coding challenge in JavaScript about quadratic functions (https://en.wikipedia.org/wiki/Quadratic_function) and how you can create a cartesian coordinate system (https://en.wikipedia.org/wiki/Cartesian_coordinate_system) in combination with eachother.
The function notation is for example: _f(x) = x² -7_, and the formula should be: _y = x² - 7 _.
And then you should be able to draw a cartesian coordinate system with this numbers. (See enclosure)

**EDIT:**

Not specific a quadratic function but just to draw a plotter.