8.F.A.3 - Interpret the equation y = mx +b as defining a linear function, whose graph is a staright line; give examples of functions that are not linear. For example, the function A = s^{2} giving the area of a square as a function of its side length is not linear becasue its graph contains the points (1,1) , (2,4) , and (3,9), which are not a straight line.