Generic equation parabola given three points

Usually, the function of a parabola is y=ax^2+bx+c. With your three given points, which I don't know, plug in your x's and y's to come up with three quadratic equations. Using those equations, you use algebra to find out what a, b, and c equal. Once you have a numerical answer, insert them in the usual quadratic function to have your answer.

This guys explains with visually with examples. Do check it out. https://www.youtube.com/watch?v=7KC8KqljahE

Hope this helps! If not, do let me know of anything you are stuck on.