This document describes a linear function model for a set of data points (x,y) with points A(0,2) and B(4,0). It finds the linear function f(x) = mx + b that best fits the line through the two points, where the slope m is -0.5 and the y-intercept b is 2. It also shows how the linear function approximation improves as more data points are included in the linear regression.