Question

discrete mathematics

1. 

Show that if a | b and b | a, where a and b are integers, then a = b or a = -b.  

//Ex. 5, Page 208.

2.

Show that if a, b, c, and d are integers such that a | c and b | d, then ab | cd.

//Ex. 6, Page 208. 

3.

What are the quotient and remainder when

a) 44 is divided by 8?

b) 777 is divided by 21?

f) 0 is divided by 17?

g) 1,234,567 is divided by 1001?   

//(a), (b), (f), and (g) Ex. 10, Page 209.

4.

Determine whether each of these integers is a prime.

a) 19

b) 27

e) 107

f) 113

//(a), (b), (e), and (f) Ex. 2, Page 217.

5.

Find the prime factorization of each of these integers.

a) 39

c) 101

d) 143

f) 899

//(a), (c), (d), and (f) Ex. 4, Page 217.

6.

What are the greatest common divisors of these pairs of integers?

a) 23 * 33 * 55 and 25 * 33 * 52

d) 22 * 7 and 53 * 13 

//(a) and (d) Ex. 20, Page 218.

7.

Find gcd(1000, 625) and lcm(1000, 625) and verify that gcd(1000, 625)*lcm(1000, 625) = 1000*625 

//Ex. 24, Page 218.

Answer 1