## Y

(0, 0) 100 200 300 400 500 600 700 (450, 0) (0, 0) 100 200 300 400 500 600 700 (450, 0) You may have encountered this difficulty when solving Practice Problem 8 in Section 8.1. If desired, we can always find the exact coordinates by treating the corresponding equations as a pair of simultaneous equations and solving them algebraically. The variable x can be eliminated by multiplying equation (2) by 30 and subtracting from (1) to get Equation (3) gives y 150 and if this value is substituted into...

## Practice Problem

5 The supply and demand equations of a good are given by The government decides to impose a tax, t, per unit. Find the value of t which maximizes the government's total tax revenue on the assumption that equilibrium conditions prevail in the market. We conclude this section by describing the use of a computer package to solve optimization problems. Although a spreadsheet could be used to do this, by tabulating the values of a function, it cannot handle the associated mathematics. A symbolic...

## Practice Problems

4 Consider the supply and demand equations We conclude that stability depends on the relative sizes of a and c, which govern the slopes of the supply and demand curves. Bearing in mind that we have chosen to consider supply and demand equations in which Q is expressed in terms of P, namely we deduce that the system is stable whenever the supply curve is flatter than the demand curve when P is plotted on the horizontal axis. Throughout this section we have concentrated on linear models. An...

## C m

To deduce that if the interest is compounded with ever-increasing frequency (that is, continuously) then 24 (Excel) The sum of 100 is invested at 12 interest for 20 years. Tabulate the value of the investment at the end of each year, if the interest is compounded (a) annually (b) quarterly (c) monthly (d) continuously Draw graphs of these values on the same diagram. Comment briefly on any similarities and differences between these graphs. 25 (Excel) A department store charges interest on any...

## ExampleEXCEL

Consider the supply and demand equations (a) Assuming that the market is in equilibrium, write down a difference equation for price. (b) Given that P0 1, find the values of the price, Pt for t 1, 2, , 10 and plot a graph of Pt against t. Describe the qualitative behaviour of the time path. 12 - Pt P 4 which rearranges to give Notice that this difference equation is not of the form considered in this section, so we cannot obtain an explicit formula for Pt in terms of t. (b) We are given that P0...