1.
2.
Define f: ZZ and 9: ZZ by f(x)=3x+1 and g(x) = x².
(a) Calculate (go f)(2).
(b) Find an explicit formula for the function gof.
Define f: R2 R2 by f(x, y) = (3x+y, 5x+2y). Give an explicit formula for f-1.
Verify that it is the inverse of f. Do not include a derivation for f¹ unless it is for the verification.
Suppose that two toothpaste companies compete for customers in a fixed market in which each
customer uses either Brand A or Brand B. Suppose also that a market analysis shows that the
buying habits of the customers fit the following pattern in the quarters that were analyzed:
each quarter (three-month period), 30% of A users will switch to B, while the rest stay with
A. Moreover, 40% of B users will switch to A in a given quarter, while the remaining B users
will stay with B. Finally assume that this pattern does not vary from quarter to quarter.
(a) If A initially has all of the customers, what are the market shares 2 quarters later?
(b) If A initially has all of the customers, what are the market shares 20 quarters later?
(c) If B initially has all of the customers, what are the market shares 2 quarters later?
(d) If B initially has all of the customers, what are the market shares 20 quarters later?
1. The regular representation of a finite group G is a pair (Vreg, Dreg). Vreg is a vector space
and Dreg is a homomorphism.
(a) What is the dimension of Vreg?
(b) Describe a basis for Vreg and give a formula for Dreg. Hence explain why the homo-
morphism property is satisfied by Dreg.
(c) Prove that the character ✗reg (g) defined by tr Dreg (g) is zero if g is not the identity
element of the group.
(d) A finite group of order 60 has five irreducible representations R1, R2, R3, R4, R5. R₁
is the trivial representation. R2, R3, R4 have dimensions (3,3,4) respectively. What is the
dimension of R5? Explain how your solution is related to the decomposition of the regular
representation as a direct sum of irreducible representations (You can assume without proof
the properties of this decomposition which have been explained in class and in the lecture
notes).
(e) A
group element
has characters in the irreducible representations R2, R3, R4 given
as
R3
R2 (g)
= -1
X³ (g) = −1 ; XR4 (g) = 0…
Chapter 2 Solutions
Finite Mathematics for Business, Economics, Life Sciences and Social Sciences
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