ECON6018 Mathematics for Economics Homework 1
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ECON6018 Mathematics for Economics
Homework 1. Chapter 2 – Equilibrium analysis
Due: 12/02/2023, 11.59pm, online in the Assignments on the course’s Elearn.
1. a. Consider the demand and supply curves
D = 240 – ¼P
S = 2P – 30
a. Find the equilibrium price P*, and the corresponding quantity Q*.
b. Suppose a tax of $4.50 per unit is imposed on the producer. How will this influence the equilibrium price?
c. Compute the total revenue obtained by the producer before the tax is imposed (R*) and after (Rˆ).
d. Use diagrams to illustrate the difference between the two market equilibria (with and without the tax).
2. a. Find the values of p and q for which the equation system
x1 + x2 + x3 = q
px1 + x2 − x3 = 5
x1 − x3 = p
has:
(i) one solution; (ii) several solutions; (iii) no solution.
b. Find an expression for the general solution of the system in case (ii).
3. a. Given A = # (, find A2, A3, + A + A2 and ( − A)( + A + A2 ) where denotes the identity matrix of order 3.
b. Use the results in (a) to find ( − A)#$ .
4. Consider a three-sector input–output model in which sector 1 is agriculture, sector 2 is manufacturing, and sector 3 is energy. Suppose that the input requirements are given by the following table:
Now suppose that final demands for the three goods are 100, 80, and 30 units, respectively. If x1, x2, and x3 denote the number of units that have to be produced in the three sectors, write down and solve the Leontief equation system for the problem (by elimination method, not by matrix inversion).
5. Let the IS equation be
Y = − i
where 1 – b is the marginal propensity to save, g is the investment sensitivity to interest rates, and A is an aggregate of exogenous variables.
Let the LM equation be
Y = − i
where k and l are income and interest sensitivity of money demand, respectively, and M0 is real money balances.
a. Write the IS-LM system in matrix form.
b. Solve for Y and i by matrix inversion. (Note: this question asks for the solution by matrix inversion because it’s a 2x2 system and inverses for 2x2 matrices are straight- forward (consult notes); you don’t have to do matrix inversion for 3x3 systems.)
6. The demand and supply functions of a two-commodity market model are as follows:
Qd1 = 18 – 3P1 + P2
Qs1 = -2 + 4P1
Qd2 = 12 + P1 – 2P2
Qs2 = -2 + 3P2
Find Pi* and Qi* (i = 1, 2). (Use fractions rather than decimals.)
7. For each real number a, let
Aa = #a 1
a. Find|Aa | as a function of a.
b. When does the equation system:
a + 1
a + 4
5
a(a) 1(1)(
(a + 1)x + (a + 1)y = b
4x + (a + 4)y + (a − 1)z = 1
c. Specify the conditions that b must satisfy for the system to have any solution when:
(i) a = 1; (ii) a = 2.
2023-02-06