MATH0034
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MATH0034
1. (a) Find all prime numbers p e N for which the equation x2 = 43p + 4 has solutions x e Z.
(b) Find all solutions to the congruence
3x3 - 2x2 + 2 = 0 mod 30.
(c) (i) Show that 5 is a primitive root mod 43. Is 5 a primitive root mod 2021? (Note that 2021=43*47.)
(ii) Does the equation 5x4 + 43 = y4 have any solutions in Z? How about 5x3 + 43 = y3 ?
(25 marks)
2. (a) Compute the Legendre Symbol ╱ 、. (Note: 863 is a prime number.) State clearly all the properties presented in the lecture notes that you are using.
(b) Let p e N be a prime number such that 7 is a quadratic residue mod p. Show that the equation 2x2 + 2x + 11 = p has no solutions in integers.
(c) Let p e N be and odd prime. Recall the Gauss sum, G(p) =a(p)1(1) ╱ 、ζp(a) ,
from lectures.
Now consider
G2 (p) :=a(p)1(1) ╱ 、ζ
Show that
G2 (p) = G(p) 令 p = 士1 mod 8.
(d) Let p e N be a prime number, p = 1 mod 12. Evaluate the sum
p塞1 ╱ 、.
(25 marks)
3. (a) Let p e N be a prime number, p 5, and let n e N. Determine the number of solutions to the congruence
5x2 + 3x + 1 = 0 mod pn .
(b) Determine whether the following series converge 3-adically or not. Justify your answer.
三 3n2 三 3n2
n=1 (n!)n , n=1 (n2 !)3 .
(c) Find a solution to each of the following congruences: x7 = 50 mod 74 ;
26p = 51 mod 55
(25 marks)
4. (a) Find 2 solutions in positive integers to the equation x2 - 26y2 = 10. (b) Find two distinct factorizations of 10 into irreducible elements in Z[^26]
and hence deduce that Z[^26] is not a unique factorization domain. (c) Let p e N be a prime number, p = 5 mod 12. Show that if pl(x2 +xy +y2 ),
for some x, y e Z, then p2 l(x2 + xy + y2 ).
(25 marks)
2022-08-04