Homework:

  1. Read Chapter 15 and complete Exercises 15.2, 15.3, 15.4, 15.7
  2. Complete the Exercises given below.

 

I will ask for volunteers to present Exercises 1 and 2 (below) in class next lesson.I will collect Exercise 3 on Thursday, November 10.

 

  1. Prove that is a multiplicative function by filling in the sketch of the proof provided below.

 

Theorem.If gcd(m, n) = 1, then .

†††††††††††

††††† Sketch of Proof.

a) Assume that m and n are two relatively prime positive integers, and prove that any divisor d of mn can be written uniquely as a product d1d2 where (d1, d2) = 1 and d1|m, d2|n.

b) Conversely, every pair of divisors d1|m, d2|n satisfying (d1, d2) = 1 gives rise to a divisor d1d2 of mn.

Hence .

 

2.†† a) Prove that if f is a multiplicative function and n has prime factorization , then

b) Deduce that if n has prime factorization , then

 

3.†† Work through parts a) through d) below to prove Eulerís Theorem.

 

Theorem (Euler).Every even perfect number is of the form where both p and are prime.

 

Proof.

a)      Suppose that n is an even perfect number and write , where s is odd.Show that and .

 

b)      Let ††Show that if t > 1, then ; that is, .

 

c)      Derive a contradiction from the fact that t > 1; hence t = 1 and ††Conclude that .

 

d)      Explain why part c) implies that prime.Conclude that r +1 must be prime too.Hence .