1. It has been conjectured that there are infinitely many primes of the form n2 – 2. Exhibit five such primes. -
1. It has been conjectured that there are infinitely many primes of the form n2 – 2. Exhibit five such primes. -
Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
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Binomial Distribution
Binomial is an algebraic expression of the sum or the difference of two terms. Before knowing about binomial distribution, we must know about the binomial theorem.
Topic Video
Question
1
![acd(a, b) = 1, there must exist integers r and s satisfying ar + bs = 1. As a result,
em 3.3. If V
a/b with
V2 = V2(ar + bs) = (v2a)r +(/2b)s = 2br + as
This representation of 2 leads us to conclude that 2 is an integer, an obvious
impossibility.
ith
PROBLEMS 3.1
1. It has been conjectured that there are infinitely many primes of the form n² – 2. Exhibit
five such primes.
2. Give an example to show that the following conjecture is not true: Every positive integer
can be written in the form p +a², where p is either a prime or 1, and a > 0.
3. Prove each of the assertions below:
(a) Any prime of the form 3n +1 is also of the form 6m +1.
(b) Each integer of the form 3n +2 has a prime factor of this form.
(c) The only prime of the form n3 - 1 is 7.
[Hint: Write n³ – 1 as (n – 1)(n² + n + 1).]
(d) The only prime p for which 3p +1 is a perfect square is p = 5.
(e) The only prime of the form n2 -4 is 5.
4. If p 2 5 is a prime number, show that p² + 2 is composite.
[Hint: p takes one of the forms 6k + 1 or 6k + 5.]
5. (a) Given that p is a prime and p|a", prove that p" | a".
(b) If gcd(a, b) = p, a prime, what are the possible values of gcd(a2, b²), gcd(a², b) and
gcd(a', b?)?
6. Establish each of the following statements:
(a) Every integer of the form n + 4, with n > 1, is composite.
[Hint: Write n* +4 as a product of two quadratic factors.]
(b) If n > 4 is composite, then n divides (n – 1)!.
(c) Any integer of the form 8" + 1, where n > 1, is composite.
[Hint: 2" +1|23n + 1.]
(d) Each integer n > 11 can be written as the sum of two composite numbers.
[Hint: If n is even, say n = 2k, then n - 6 = 2(k – 3); for n odd, consider the integer
n- 9.]
7. Find all prime numbers that divide 50!.
8. If p >q > 5 and p and q are both primes, prove that 24 | p2 –- q².
9. (a) An unanswered question is whether there are infinitely many primes that are 1 more
than a power of 2, such as 5 = 22 + 1. Find two more of these primes.
(b) A more general conjecture is that there exist infinitely many primes of the form
n2 + 1; for example, 257 = 162 + 1. Exhibit five more primes of this type.
10. If p +5 is an odd prime, prove that either p2 – 1 or p² +1 is divisible by 10.
11. Another unproven conjecture is that there are an infinitude of primes that are 1 less than
a power of 2, such as 3 = 2² – 1.
(a) Find four more of these primes.
(b) If p = 2k - 1 is prime, show that k is an odd integer, except when k == 2.
[Hint: 314"-1 for all n > 1.]
12. Find the prime factorization of the integers 1234, 10140, and 36000.
13. If n > 1 is an integer not of the form 6k + 3, prove that nº + 2" is composite
[Hint: Show that either 2 or 3 divides n2+ 2".]](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F7dbb4ae4-0d65-4baa-9481-63f79be91eca%2Fdc2ffb96-b11b-4cb2-ba17-492467962a94%2Fui2yxoq_processed.jpeg&w=3840&q=75)
Transcribed Image Text:acd(a, b) = 1, there must exist integers r and s satisfying ar + bs = 1. As a result,
em 3.3. If V
a/b with
V2 = V2(ar + bs) = (v2a)r +(/2b)s = 2br + as
This representation of 2 leads us to conclude that 2 is an integer, an obvious
impossibility.
ith
PROBLEMS 3.1
1. It has been conjectured that there are infinitely many primes of the form n² – 2. Exhibit
five such primes.
2. Give an example to show that the following conjecture is not true: Every positive integer
can be written in the form p +a², where p is either a prime or 1, and a > 0.
3. Prove each of the assertions below:
(a) Any prime of the form 3n +1 is also of the form 6m +1.
(b) Each integer of the form 3n +2 has a prime factor of this form.
(c) The only prime of the form n3 - 1 is 7.
[Hint: Write n³ – 1 as (n – 1)(n² + n + 1).]
(d) The only prime p for which 3p +1 is a perfect square is p = 5.
(e) The only prime of the form n2 -4 is 5.
4. If p 2 5 is a prime number, show that p² + 2 is composite.
[Hint: p takes one of the forms 6k + 1 or 6k + 5.]
5. (a) Given that p is a prime and p|a", prove that p" | a".
(b) If gcd(a, b) = p, a prime, what are the possible values of gcd(a2, b²), gcd(a², b) and
gcd(a', b?)?
6. Establish each of the following statements:
(a) Every integer of the form n + 4, with n > 1, is composite.
[Hint: Write n* +4 as a product of two quadratic factors.]
(b) If n > 4 is composite, then n divides (n – 1)!.
(c) Any integer of the form 8" + 1, where n > 1, is composite.
[Hint: 2" +1|23n + 1.]
(d) Each integer n > 11 can be written as the sum of two composite numbers.
[Hint: If n is even, say n = 2k, then n - 6 = 2(k – 3); for n odd, consider the integer
n- 9.]
7. Find all prime numbers that divide 50!.
8. If p >q > 5 and p and q are both primes, prove that 24 | p2 –- q².
9. (a) An unanswered question is whether there are infinitely many primes that are 1 more
than a power of 2, such as 5 = 22 + 1. Find two more of these primes.
(b) A more general conjecture is that there exist infinitely many primes of the form
n2 + 1; for example, 257 = 162 + 1. Exhibit five more primes of this type.
10. If p +5 is an odd prime, prove that either p2 – 1 or p² +1 is divisible by 10.
11. Another unproven conjecture is that there are an infinitude of primes that are 1 less than
a power of 2, such as 3 = 2² – 1.
(a) Find four more of these primes.
(b) If p = 2k - 1 is prime, show that k is an odd integer, except when k == 2.
[Hint: 314"-1 for all n > 1.]
12. Find the prime factorization of the integers 1234, 10140, and 36000.
13. If n > 1 is an integer not of the form 6k + 3, prove that nº + 2" is composite
[Hint: Show that either 2 or 3 divides n2+ 2".]
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