Math 3124 Friday, September 26
Fourth Homework
Due 9:05 a.m., Friday October 3
1. The invalid ISBN 0-669-03925-6 is the result of a transposition of two adjacent digits.
Determine the correct ISBN. (2 points)
2. Compute the order of [1] [2]
[0] [4]in GL(2,Z5). (2 points)
3. Let Gbe a group in which every nonidentity element has order 2. Prove that Gis
abelian. Hint: first show that a2=b2=abab =efor all a,b∈G. (2 points)
4. Problem 14.31 on page 81. (2 points)
(4 problems, 8 points altogether)