He linear function is popular in economics. It is attractive because it is simple and easy to handle mathematically. It has many important applications. Linear functions are those whose graph is a straight line. to make a straight line the y and x values must have common ratioonly first table is a linear function common ratio for x = 1 - 0 =1= 2 -1 = 1 common ratio for y = 5 -3 = 2= 7 - 5 = 2