The following sets are used in this book:

• The set of natural numbers, N = {1, 2, 3,⋯}.
• The set of integers, Z = {⋯,−3,−2,−1, 0, 1, 2, 3,⋯}.
• The set of rational numbers Q.
• The set of real numbers R.
• Closed intervals on the real line. For example, [2, 3] is the set of all real numbers x such that 2 ≤ x ≤ 3.
• Open intervals on the real line. For example (−1, 3) is the set of all real numbers x such that −1 < x < 3.
• Similarly, [1, 2) is the set of all real numbers x such that 1 ≤ x < 2.
• The set of complex numbers C is the set of numbers in the form of a + bi, where a, b ∈ R, and i = √−1.