Quadratic model
This diagram shows the flexibility of a quadratic model.
y = b0 + b1 x + b2 x2
The equation has 3 parameters so it is defined by the position of 3 points on the curve. Drag the 3 red arrows to fit the quadratic model close to the data points.
Click Show residuals to show them and explain that we want to make them small. Click Least squares to minimise the sum of squared residuals.