Number of diagonals in a polygon, number of squares in special figures, triangular numbers are just some of the examples how we can model with quadratic functions. Using difference tables to establish the pattern and confirm the relationship in Geogebra. Enter the numbers in a spreadsheet, draw a graph, fit a polynomial regression model, use the model for predictions. An assessment task on direct and inverse variation to follow the lesson. The zipped folder includes Geogebra files. Teacher handout has full instructions how to use Geogebra. A lesson can be differentiated: stronger students attempting difference tables and taking an algebraic approach; weaker students using technology to arrive at the same answer.