The tool I used for modellin is MS Excel. As you on the left side of the picture, I tabulate the x and y coordinates with respect to their columns. Then, I plotted it using the scatter plot graph. In this type of graph, only plots are drawn on the Cartesian plane. Next, I created a trendline as represented by the blue dashed line. There are options to the degree of your trendline: linear, polynomial or exponential. The closes fit is the polynomial with a degree of 2. An option is listed there in displaying the equation. The equation modelled by regression through data fitting is:
y = x² - 4x+1
y = x² - 4x+1