A linear function is a function of the form f(x) = mx + b whose graph is a straight line. When written in this form, the slope of the graph is m and the y-intercept is b. Except for constant functions, linear functions are the simplest of all mathematical functions. This is because the largest exponent of the variable x is 1 in a linear function. So a linear function is sometimes said to be a polynomial function of degree 1. In general, polynomial functions that have degree higher than 1 have more complicated graphs and require a higher level of mathematical analysis than do linear functions. The simplest linear functions are those which pass through the origin. They have y-intercept equal to 0, so their equations take the form f(x) = mx, or, equivalently, y = mx. The slope m in this equation is calculated as follows: Pick two points on...