Congruences and Divisibility Criteria (1.15-1.24)

• Exercise 1.15. Does the converse hold?
• Exercise 1.16.
• Exercise 1.17.
• Exercise 1.18. Look up “principle of mathematical induction” for this one.
• Question 1.20. This is the same question posed alongside theorem 1.14.
• Theorem 1.21. Carry out some specific examples of this.
• Theorems 1.22 and 1.23.
• Theorem 1.24.