You improve your time running a course by 5 seconds in week one, by 3 seconds in week two, and by 4 seconds in week three. What is the mean weekly change in your running time?

Suppose that the price p, in dollars, and the number of sales, x, of a certain item follow the equation 4 p plus 4 x plus 2 pxequals56. suppose also that p and x are both functions of time, measured in days. find the rate at which x is changing when xequals2, pequals6, and startfraction dp over dt endfraction equals1.5.