MAT 421 Suggested HW Problems

Highlighted homework is due soon

Date

Assignment
Material for Test 2 ends here (Chapter 37)
29 July Use case analysis to show that if \(|x+y|\leq|a|\), then \(|x|\leq|a|+|y|\).
Show that 3 is prime in \(\mathbb{Z}[\,i\sqrt 5\,]\) — use the same strategy I used to show 2 is prime in \(\mathbb{Z}[\,i\sqrt{5}\,]\)
35.3, 35.4, 35.6, 36.2, 36.3, 36.4, 36.5, 37.1, 37.2, 37.3 (need \(i\) for (d)), 37.5, 37.6, 37.8
Extra Credit: 35.9
22 July 16.1, 16.3, 17.1, 17.2, 17.4, 18.1 (started in class), 18.2
Divide (i.e., find quotient and remainder) the Gaussian integers:
  1. \(20+3i\) by \(-1+7i\)
  2. \(36-21i\) by \(3+4i\)
Hints:
17.4 Factor out the gcd, solve the new problem, use it to construct a solution to the original.
20 July Read Chapter 37
15 July Read Chapters 35, 36
14., 14.2
The extra credit mentioned in class: if \(\gcd(m,n)=1\) and \(x\) divides \(mn\) and \(x\equiv_m a\) and \(x\equiv_n b\) then \(a\mid m\) and \(b\mid n\). (Note: The statement is false! Find a counterexample instead.)
15.2, 15.3, 15.5, 15.6
Hints:
14.1 Consider the case where \(n\) is odd, so that \(x^n+1=(x+1)(x^{n-1}-x^{n-2}+x^{n-3}-x^{n-4}+\cdots-x+1)\), then the case where \(n\) is even, but not a power of 2, in which case \(n=q\cdot 2^k\), where \(q\) is odd.

14.2 Try an example, say \(m=3\) and \(k=4\), then \(m=3\) and \(k=5\). Look for a pattern to the division of \(F_{k-2}\) by \(F_m\). Then show that, for any odd number, \(\gcd(a,a-2)=1\).

13 July Read Chapter 18
8 JulyRead Chapter 16
Prove that any prime number larger than 4 is congruent to 1 or 5 modulo 6
11.5, 11.6, 12.2, 13.3, (for graduates: 13.6)
Extra Credit: 12.6, 13.2, (for undergraduates:) 13.6
6 JulyRead Chapter 14
Material for Test 1 ends here
1 July9.1, 9.3, 10.1, 10.2, 11.1, 11.2, 11.3, 11.10
24 JunRead Ch. 9
7.1, 7.2, 7.3, 8.2, 8.3, 8.4 (b)–(e), 8.5, 8.9
17 JunRead Ch. 7
5.1, 5.3, 5.4, 6.1, 6.2, 6.5, 6.6
10 Jun2.2, 2.6, 2.7, 3.1, 3.2, 3.3
3 Jun1.1, 1.2, 1.6