We can find the slope of a line between two points as long as we know the coordinates of both points. Since these two points lie on a function whose equation we know, we can use the function to determine the coordinates of the points. When x = 2 we have f(2) = (2)^{2} = 4, so the coordinates of the first point are (2, 4). When x = 4 we have f(4) = (4)^{2} = 16 so the coordinates of the second point are (4, 16). Now that we know the coordinates of both points we can calculate the rise and run: We have rise = 16  4 = 12 and run = 4  2 = 2. The slope of the line between these two points is To think of this in a more formulaoriented way, we have a = 2 and b = 4, so f(a) = 4 and f(b) = 16. Then the slope of the line between the two points is
